WorldWideScience

Sample records for chlorophyll antenna size

  1. Modulation of the light-harvesting chlorophyll antenna size in Chlamydomonas reinhardtii by TLA1 gene over-expression and RNA interference

    Science.gov (United States)

    Mitra, Mautusi; Kirst, Henning; Dewez, David; Melis, Anastasios

    2012-01-01

    Truncated light-harvesting antenna 1 (TLA1) is a nuclear gene proposed to regulate the chlorophyll (Chl) antenna size in Chlamydomonas reinhardtii. The Chl antenna size of the photosystems and the chloroplast ultrastructure were manipulated upon TLA1 gene over-expression and RNAi downregulation. The TLA1 over-expressing lines possessed a larger chlorophyll antenna size for both photosystems and contained greater levels of Chl b per cell relative to the wild type. Conversely, TLA1 RNAi transformants had a smaller Chl antenna size for both photosystems and lower levels of Chl b per cell. Western blot analyses of the TLA1 over-expressing and RNAi transformants showed that modulation of TLA1 gene expression was paralleled by modulation in the expression of light-harvesting protein, reaction centre D1 and D2, and VIPP1 genes. Transmission electron microscopy showed that modulation of TLA1 gene expression impacts the organization of thylakoid membranes in the chloroplast. Over-expressing lines showed well-defined grana, whereas RNAi transformants possessed loosely held together and more stroma-exposed thylakoids. Cell fractionation suggested localization of the TLA1 protein in the inner chloroplast envelope and potentially in association with nascent thylakoid membranes, indicating a role in Chl antenna assembly and thylakoid membrane biogenesis. The results provide a mechanistic understanding of the Chl antenna size regulation by the TLA1 gene. PMID:23148270

  2. Maximizing photosynthetic productivity and solar conversion efficiency in microalgae by minimizing the light-harvesting chlorophyll antenna size of the photosystems

    Energy Technology Data Exchange (ETDEWEB)

    Melis, A.; Neidhardt, J.; Benemann, J.R. [Univ. of California, Berkeley, CA (United States). Dept. of Plant and Microbial Biology

    1998-08-01

    The solar conversion efficiency and productivity of photosynthesis in light-acclimated Dunaliella salina (green algae) were analyzed. Cells were grown under continuous low-light (LL; 100 {micro}mol photons/m{sup 2} s) or high-light (HL; 2,000 {micro}mol photons/m{sup 2} s) conditions. HL-grown cells exhibited signs of chronic photoinhibition, i.e., a lower pigment content, a highly truncated chlorophyll (Chl) antenna size for the photosystems, and accumulation of photodamaged photosystem-II (PSII) reaction centers in the chloroplast thylakoids. In spite of these deficiencies, high-light-grown cells showed photosynthetic productivity (300 mmol O{sub 2}/(mol Chl) s) that was {approximately} 3 times greater than that of the normally pigmented LL-grown cells ({approximately} 100 mmol O{sub 2}/(mol Chl) s). Recovery from photoinhibition in the HL-grown cells, induced in the absence of a light-harvesting Chl antenna size enlargement, increased photosynthetic productivity further to {approximately} 650 mmol O{sub 2}/(mol Chl) s. It is shown that, under moderate to high light conditions, D. salina with a highly truncated Chl antenna size will display superior photosynthetic productivity, solar conversion efficiency and H{sub 2} production when compared to the normally pigmented control cells. Estimates of H{sub 2} production in mass culture suggest an average of 200 L H{sub 2}/m{sup 2} d for the cells with the truncated Chl antenna, and less than 50 L H{sub 2}/m{sup 2} d for the normally pigmented cells.

  3. Vertical Meandering Approach for Antenna Size Reduction

    OpenAIRE

    Li Deng; Shu-Fang Li; Ka-Leung Lau; Quan Xue

    2012-01-01

    A novel vertical meandering technique to reduce the lateral size of a planar printed antenna is presented. It is implemented by dividing a conventional spiral patch into a different number of segments and placing them on different sides of the microwave substrate with vias as the connections. To confirm the validity of this technique, measured electrical performance and radiation characteristics of five antennas with different numbers of segments are compared. The smallest antenna is reduced ...

  4. Photoprotective Energy Dissipation in Higher Plants Involves Alteration of the Excited State Energy of the Emitting Chlorophyll(s) in the Light Harvesting Antenna II (LHCII)*

    OpenAIRE

    Johnson, Matthew P.; Ruban, Alexander V.

    2009-01-01

    Non-photochemical quenching (NPQ), a mechanism of energy dissipation in higher plants protects photosystem II (PSII) reaction centers from damage by excess light. NPQ involves a reduction in the chlorophyll excited state lifetime in the PSII harvesting antenna (LHCII) by a quencher. Yet, little is known about the effect of the quencher on chlorophyll excited state energy and dynamics. Application of picosecond time-resolved fluorescence spectroscopy demonstrated that NPQ involves a red-shift ...

  5. Tracing the evolution of the light-harvesting antennae in chlorophyll a/b-containing organisms.

    Science.gov (United States)

    Koziol, Adam G; Borza, Tudor; Ishida, Ken-Ichiro; Keeling, Patrick; Lee, Robert W; Durnford, Dion G

    2007-04-01

    The light-harvesting complexes (LHCs) of land plants and green algae have essential roles in light capture and photoprotection. Though the functional diversity of the individual LHC proteins are well described in many land plants, the extent of this family in the majority of green algal groups is unknown. To examine the evolution of the chlorophyll a/b antennae system and to infer its ancestral state, we initiated several expressed sequence tag projects from a taxonomically broad range of chlorophyll a/b-containing protists. This included representatives from the Ulvophyceae (Acetabularia acetabulum), the Mesostigmatophyceae (Mesostigma viride), and the Prasinophyceae (Micromonas sp.), as well as one representative from each of the Euglenozoa (Euglena gracilis) and Chlorarachniophyta (Bigelowiella natans), whose plastids evolved secondarily from a green alga. It is clear that the core antenna system was well developed prior to green algal diversification and likely consisted of the CP29 (Lhcb4) and CP26 (Lhcb5) proteins associated with photosystem II plus a photosystem I antenna composed of proteins encoded by at least Lhca3 and two green algal-specific proteins encoded by the Lhca2 and 9 genes. In organisms containing secondary plastids, we found no evidence for orthologs to the plant/algal antennae with the exception of CP29. We also identified PsbS homologs in the Ulvophyceae and the Prasinophyceae, indicating that this distinctive protein appeared prior to green algal diversification. This analysis provides a snapshot of the antenna systems in diverse green algae, and allows us to infer the changing complexity of the antenna system during green algal evolution. PMID:17307901

  6. Predicting crappie recruitment in Ohio reservoirs with spawning stock size, larval density, and chlorophyll concentrations

    Science.gov (United States)

    Bunnell, David B.; Hale, R. Scott; Vanni, Michael J.; Stein, Roy A.

    2006-01-01

    Stock-recruit models typically use only spawning stock size as a predictor of recruitment to a fishery. In this paper, however, we used spawning stock size as well as larval density and key environmental variables to predict recruitment of white crappies Pomoxis annularis and black crappies P. nigromaculatus, a genus notorious for variable recruitment. We sampled adults and recruits from 11 Ohio reservoirs and larvae from 9 reservoirs during 1998-2001. We sampled chlorophyll as an index of reservoir productivity and obtained daily estimates of water elevation to determine the impact of hydrology on recruitment. Akaike's information criterion (AIC) revealed that Ricker and Beverton-Holt stock-recruit models that included chlorophyll best explained the variation in larval density and age-2 recruits. Specifically, spawning stock catch per effort (CPE) and chlorophyll explained 63-64% of the variation in larval density. In turn, larval density and chlorophyll explained 43-49% of the variation in age-2 recruit CPE. Finally, spawning stock CPE and chlorophyll were the best predictors of recruit CPE (i.e., 74-86%). Although larval density and recruitment increased with chlorophyll, neither was related to seasonal water elevation. Also, the AIC generally did not distinguish between Ricker and Beverton-Holt models. From these relationships, we concluded that crappie recruitment can be limited by spawning stock CPE and larval production when spawning stock sizes are low (i.e., CPE , 5 crappies/net-night). At higher levels of spawning stock sizes, spawning stock CPE and recruitment were less clearly related. To predict recruitment in Ohio reservoirs, managers should assess spawning stock CPE with trap nets and estimate chlorophyll concentrations. To increase crappie recruitment in reservoirs where recruitment is consistently poor, managers should use regulations to increase spawning stock size, which, in turn, should increase larval production and recruits to the fishery.

  7. Non-photochemical quenching in cryptophyte alga Rhodomonas salina is located in chlorophyll a/c antennae.

    Science.gov (United States)

    Kaňa, Radek; Kotabová, Eva; Sobotka, Roman; Prášil, Ondřej

    2012-01-01

    Photosynthesis uses light as a source of energy but its excess can result in production of harmful oxygen radicals. To avoid any resulting damage, phototrophic organisms can employ a process known as non-photochemical quenching (NPQ), where excess light energy is safely dissipated as heat. The mechanism(s) of NPQ vary among different phototrophs. Here, we describe a new type of NPQ in the organism Rhodomonas salina, an alga belonging to the cryptophytes, part of the chromalveolate supergroup. Cryptophytes are exceptional among photosynthetic chromalveolates as they use both chlorophyll a/c proteins and phycobiliproteins for light harvesting. All our data demonstrates that NPQ in cryptophytes differs significantly from other chromalveolates - e.g. diatoms and it is also unique in comparison to NPQ in green algae and in higher plants: (1) there is no light induced xanthophyll cycle; (2) NPQ resembles the fast and flexible energetic quenching (qE) of higher plants, including its fast recovery; (3) a direct antennae protonation is involved in NPQ, similar to that found in higher plants. Further, fluorescence spectroscopy and biochemical characterization of isolated photosynthetic complexes suggest that NPQ in R. salina occurs in the chlorophyll a/c antennae but not in phycobiliproteins. All these results demonstrate that NPQ in cryptophytes represents a novel class of effective and flexible non-photochemical quenching. PMID:22235327

  8. Excitation energy transfer in intact cells and in the phycobiliprotein antennae of the chlorophyll d containing cyanobacterium Acaryochloris marina.

    Science.gov (United States)

    Theiss, Christoph; Schmitt, Franz-Josef; Pieper, Jörg; Nganou, Collins; Grehn, Moritz; Vitali, Marco; Olliges, Rachel; Eichler, Hans Joachim; Eckert, Hann-Jörg

    2011-08-15

    The cyanobacterium Acaryochloris marina is unique because it mainly contains Chlorophyll d (Chl d) in the core complexes of PS I and PS II instead of the usually dominant Chl a. Furthermore, its light harvesting system has a structure also different from other cyanobacteria. It has both, a membrane-internal chlorophyll containing antenna and a membrane-external phycobiliprotein (PBP) complex. The first one binds Chl d and is structurally analogous to CP43. The latter one has a rod-like structure consisting of three phycocyanin (PC) homohexamers and one heterohexamer containing PC and allophycocyanin (APC). In this paper, we give an overview on the investigations of excitation energy transfer (EET) in this PBP-light-harvesting system and of charge separation in the photosystem II (PS II) reaction center of A. marina performed at the Technische Universität Berlin. Due to the unique structure of the PBP antenna in A. marina, this EET occurs on a much shorter overall time scale than in other cyanobacteria. We also briefly discuss the question of the pigment composition in the reaction center (RC) of PS II and the nature of the primary donor of the PS II RC. PMID:21396735

  9. Novel small-size directional antenna for UWB WBAN/WPAN applications

    OpenAIRE

    Klemm, M.; Kovacs, Istvan Z.; Gert F. Pedersen; Troster, Gerhard

    2005-01-01

    This paper presents a novel small-size directional antenna design for ultrawide-band wireless body area networks/wireless personal area networks applications. The design is based on a typical slot antenna structure with an added reflector in order to achieve directionality. The effects of different antenna parameters and human body proximity on the radiation characteristics are analyzed. Antenna measurements with an optic RF setup were performed in order to characterize the small-size antenna...

  10. A SIZE-REDUCED LOG PERIODIC DIPOLE ANTENNA

    Institute of Scientific and Technical Information of China (English)

    Yang Zhengguang; Su Donglin; Lü Shanwei

    2006-01-01

    A rectangle capacity patch was adopted as the resonance unit of the Log Periodic Dipole Antenna (LPDA) so as to realize the miniaturization of this aerial in this paper. Fifteen rectangle capacity patch units of different parameters were analyzed in this paper and three design laws of size-reduction were found. According to these design laws, a 70% miniaturization ratio LPDA was designed and fabricated. The Voltage Standing Wave Ratio (VSWR) and pattern of the fabricated LPDA were measured. The results indicate that this size-reduction method do not deteriorate performance.

  11. Differentiation between heterotrophic and photosynthetic plankton by size fractionation, glucose uptake, ATP and chlorophyll content

    International Nuclear Information System (INIS)

    By means of a technique which included 3H-D-glucose uptake, ATP and chlorophyll analyses in different size fractions of lake water microorganisms, the bacterial and the phytoplankton biomasses were estimated from four eutrophic lakes. Short term glucose uptake experiments and chlorophyll analyses in lake water used as indicators of the bacteria and the phytoplankton present in the different size fractions, whereas ATP measurements were used to quantify their respective biomasses. The bacteria comprised between 3 and 18% of total biomass (phytoplankton + bacteria) and between 50 and 90% of the bacteria were free-living. The numbers of bacteria calculated from the bacterial ATP content were 20 to 50% higher than the numbers estimated by direct counting. (author)

  12. Two-photon excited fluorescence from higher electronic states of chlorophylls in photosynthetic antenna complexes a new approach to detect strong excitonic chlorophyll a/b coupling

    CERN Document Server

    Leupold, D; Ehlert, J; Irrgang, K D; Renger, G; Lokstein, H

    2002-01-01

    Stepwise two-photon excitation of chlorophyll a and b in the higher plant main light-harvesting complex (LHC II) and the minor complex CP29 (as well as in organic solution) with 100-fs pulses in the Q/sub y/ region results in a weak blue fluorescence. The dependence of the spectral shape of the blue fluorescence on excitation wavelength offers a new approach to elucidate the long-standing problem of the origin of spectral "chlorophyll forms" in pigment-protein complexes, in particular the characterization of chlorophyll a/b-heterodimers. As a first result we present evidence for the existence of strong chlorophyll a/b-interactions (excitonically coupled transitions at 650 and 680 nm) in LHC II at ambient temperature. In comparison with LHC II, the experiments with CP29 provide further evidence that the lowest energy chlorophyll a transition (at ~680 nm) is not excitonically coupled to chlorophyll b. (22 refs).

  13. Synthesis of self-aggregative zinc chlorophylls possessing polymerizable esters as a atable model compound for main light-harvesting antennas of green photosynthetic bacteria

    OpenAIRE

    Reiko Shibata; Kazuya Nishihara; Hitoshi Tamiaki

    2006-01-01

    Zinc bacteriochlorophyll-d derivatives possessing a polymerizable moiety at the 17-propionate were prepared as model compounds of natural occurring chlorophylls in the main peripheral antennas of green photosynthetic bacteria (chlorosomes). The synthetic compounds self-aggregated in nonpolar organic solvents as well as in the solid state to give large oligomers similar to chlorosomal J-aggregates. Such introduction of the polymerizable groups in the ester did not suppress the ability of ...

  14. Radiation Characteristics of Chlamydomonas reinhardtii CC125 and Its Truncated Chlorophyll Antenna Transformants tla1, tlaX, and 37RP1-tla1

    OpenAIRE

    Berberoglu, Halil; Pilon, Laurent; Melis, Anastasios

    2008-01-01

    This experimental study reports, for the first time, the radiation characteristics of the unicellular green algae Chlamydomonas reinhardtii strain CC125 and its truncated chlorophyll antenna transformants tla1, tlaX, and tla1-CW+. Photobiological hydrogen production is a sustainable alternative to thermochemical and electrolytic technologies with the possible advantage of carbon dioxide mitigation. However, scale-up of photobioreactors from bench top to industrial scale is made difficult by e...

  15. Two-photon excited fluorescence from higher electronic states of chlorophylls in photosynthetic antenna complexes: a new approach to detect strong excitonic chlorophyll a/b coupling.

    OpenAIRE

    Leupold, Dieter; Teuchner, Klaus; Ehlert, Jürgen; Irrgang, Klaus-Dieter; Renger, Gernot; Lokstein, Heiko

    2002-01-01

    Stepwise two-photon excitation of chlorophyll a and b in the higher plant main light-harvesting complex (LHC II) and the minor complex CP29 (as well as in organic solution) with 100-fs pulses in the Q(y) region results in a weak blue fluorescence. The dependence of the spectral shape of the blue fluorescence on excitation wavelength offers a new approach to elucidate the long-standing problem of the origin of spectral "chlorophyll forms" in pigment-protein complexes, in particular the charact...

  16. Lutein is needed for efficient chlorophyll triplet quenching in the major LHCII antenna complex of higher plants and effective photoprotection in vivo under strong light

    Directory of Open Access Journals (Sweden)

    Havaux Michel

    2006-12-01

    Full Text Available Abstract Background Lutein is the most abundant xanthophyll in the photosynthetic apparatus of higher plants. It binds to site L1 of all Lhc proteins, whose occupancy is indispensable for protein folding and quenching chlorophyll triplets. Thus, the lack of a visible phenotype in mutants lacking lutein has been surprising. Results We have re-assessed the lut2.1 phenotypes through biochemical and spectroscopic methods. Lhc proteins from the lut2.1 mutant compensate the lack of lutein by binding violaxanthin in sites L1 and L2. This substitution reduces the capacity for regulatory mechanisms such as NPQ, reduces antenna size, induces the compensatory synthesis of Antheraxanthin + Zeaxanthin, and prevents the trimerization of LHCII complexes. In vitro reconstitution shows that the lack of lutein per se is sufficient to prevent trimerization. lut2.1 showed a reduced capacity for state I – state II transitions, a selective degradation of Lhcb1 and 2, and a higher level of photodamage in high light and/or low temperature, suggesting that violaxanthin cannot fully restore chlorophyll triplet quenching. In vitro photobleaching experiments and time-resolved spectroscopy of carotenoid triplet formation confirmed this hypothesis. The npq1lut2.1 double mutant, lacking both zeaxanthin and lutein, is highly susceptible to light stress. Conclusion Lutein has the specific property of quenching harmful 3Chl* by binding at site L1 of the major LHCII complex and of other Lhc proteins of plants, thus preventing ROS formation. Substitution of lutein by violaxanthin decreases the efficiency of 3Chl* quenching and causes higher ROS yield. The phenotype of lut2.1 mutant in low light is weak only because rescuing mechanisms of photoprotection, namely zeaxanthin synthesis, compensate for the ROS production. We conclude that zeaxanthin is effective in photoprotection of plants lacking lutein due to the multiple effects of zeaxanthin in photoprotection, including ROS

  17. Compact-Size Low-Profile Wideband Circularly Polarized Omnidirectional Patch Antenna With Reconfigurable Polarizations

    OpenAIRE

    Cai, Yuan-Ming; Gao, Steven; Yin, Yingzeng; Li, Wenting; Luo, Qi

    2016-01-01

    A compact-size low-profile wideband circularly polarized (CP) omnidirectional antenna with reconfigurable polarizations is presented in this communication. This design is based on a low-profile omnidirectional CP antenna which consists of a vertically polarized microstrip patch antenna working in TM01/TM02 modes and sequentially bended slots etched on the ground plane for radiating horizontally polarized electric field. The combined radiation from both the microstrip patch and the slots leads...

  18. Dual-frequency Circularly-polarized Patch Antenna with Compact Size and Small Frequency Ratio

    OpenAIRE

    Bao, Xiulong; Ammann, Max

    2007-01-01

    A novel probe-fed single-layer annular-ring patch antenna for dual-frequency circular polarization is evaluated numerically and experimentally verified. The proposed antenna consists of a small circular patch surrounded by two concentric annular-rings, which is loaded by an unequal lateral cross-slot ground plane. The circularly-polarized frequency ratio of the two resonant modes is tunable to a small value, suitable for wireless communications systems. The patch size of the proposed antenna ...

  19. Small-Size Meandered Loop Antenna for WLAN Dongle Devices

    OpenAIRE

    Wen-Shan Chen; Chien-Min Cheng; Da-Huei Lee; Chun-Lin Ciou; Wei-Syun Sin; Guang-Yuan Cai

    2014-01-01

    This paper proposes a loop-type USB dongle antenna, which is fabricated on a 1.6 mm thick FR-4 substrate for WLAN band systems. The front side of substrate consists of a 50-ohm coaxial line and a multiarm monopole antenna, while the back side has a meandered loop antenna connected to the ground by two via holes. The meandered loop resonates half-wavelength mode at about 2.4 GHz and its higher modes. The higher modes excited by the multiarm monopole form the 5.2 GHz frequency band. The bandwid...

  20. Novel type of red-shifted chlorophyll a antenna complex from Chromera velia: II. Biochemistry and spectroscopy

    Czech Academy of Sciences Publication Activity Database

    Bína, David; Gardian, Zdenko; Herbstová, Miroslava; Kotabová, Eva; Koník, P.; Litvín, Radek; Prášil, Ondřej; Tichý, Josef; Vácha, František

    2014-01-01

    Roč. 1837, č. 6 (2014), s. 802-810. ISSN 0005-2728 R&D Projects: GA ČR GBP501/12/G055 Institutional support: RVO:60077344 ; RVO:61388971 Keywords : Chromera velia * red-shifted chlorophyll * Chlorophyll fluorescence Subject RIV: CE - Biochemistry; CE - Biochemistry (MBU-M) Impact factor: 5.353, year: 2014

  1. High Isolation and Low Correlation Small Size Multi-Antenna for MIMO Mobile Terminals

    Institute of Scientific and Technical Information of China (English)

    2012-01-01

    A new method of forming a four-port multi-antenna by a two-unit patch antenna array is proposed to design a high isolation low correlation stroll size multi-antenna. Dual polarization is real-ized by the method of feeding in two ports. Defec-ted Ground Structure (DGS) is used to eliminate the coupling between the two antenna units. The test results show that the isolation between two ports reaches around 20dB, and that the antenna correlation coefficients is less than 0. 5, which meets the requirements of future mobile communi-cation systems and provides a solution to multi-antenna of MIMO terminals.

  2. Low-energy chlorophyll states in the CP43 antenna protein complex: simulation of various optical spectra. II.

    Science.gov (United States)

    Reppert, Mike; Zazubovich, Valter; Dang, Nhan C; Seibert, Michael; Jankowiak, Ryszard

    2008-08-14

    The CP43 protein complex of the core antenna of higher plant photosystem II (PSII) has two quasidegenerate "red" absorption states. It has been shown in the accompanying paper I (Dang, N. C., et al. J. Phys. Chem. B 2008, 112, 9921.) that the site distribution functions (SDFs) of red-states A and B are uncorrelated and the narrow holes are burned in subpopulations of chlorophylls (Chls) from states A and B that are the lowest-energy pigments in their particular CP43 complexes and cannot further transfer energy downhill. In this work, we present the results of a series of Monte Carlo simulations using the 3.0-A structure of the PSII core complex from cyanobacteria (Loll, B., et al. Nature 2005, 303, 1040.) to model absorption, emission, persistent, and transient hole burned (HB) spectra. At the current structural resolution, we found calculated site energies (obtained from INDO/S calculations) to be only suggestive because their values are different for the two monomers of CP43 in the PS II dimer. As a result, to probe the excitonic structure, a simple fitting procedure was employed to optimize Chl site energies from various starting values corresponding to different A/B pigment combinations to provide simultaneously good fits to several types of optical spectra. It is demonstrated that the shape of the calculated absorption, emission, and transient/persistent hole-burned spectra is consistent with experimental data and our model for excitation energy transfer between two quasi-degenerate lowest-E states (A and B) with uncorrelated SDFs discussed in paper I. Calculations revealed that absorption changes observed near 670 nm in the non-line-narrowed persistent HB spectra (assigned to photoconversion involving Chl-protein hydrogen-bonding by Hughes (Biochemistry 2006, 45, 12345.) are most likely the result of nonphotochemical hole-burning (NPHB) accompanied by the redistribution of oscillator strength due to modified excitonic interactions. We argue that a unique

  3. Phytoplankton size class derived from phytoplankton absorption and chlorophyll-a concentrations in the northern South China Sea

    Institute of Scientific and Technical Information of China (English)

    WANG Guoqing; CAO Wenxi; WANG Guifen; ZHOU Wen

    2013-01-01

    A previously developed model was modified to derive three phytoplankton size classes (micro-,nano-,and pico-phytoplankton) from the overall chlorophyll-a concentration,assuming that each class has a specific absorption coefficient.The modified model performed well using in-situ data from the northern South China Sea,and the results were reliable and accurate.The relative errors of the size-fractioned chlorophyll-a concentration for each size class were:micro-:21%,nano-:41%,pico-:26%,and nano+pico:23%.The model was then applied on ocean color remote sensing data to examine the distribution and variation of phytoplankton size classes in northern South China Sea on a large scale.

  4. Size-fractionated Chlorophyll a biomass in the northern South China Sea in summer 2014

    Science.gov (United States)

    Liu, Haijiao; Xue, Bing; Feng, Yuanyuan; Zhang, Rui; Chen, Mianrun; Sun, Jun

    2016-07-01

    Spatial distribution of phaeopigment and size-fractionated chlorophyll a (Chl a) concentrations were examined in relation to hydrographic conditions in the northern South China Sea (NSCS) during a survey from 20 August to 12 September, 2014. The total Chl a concentration varied from 0.006 to 1.488 µg/L with a mean value of 0.259±0.247 (mean±standard deviation) µg/L. Chl a concentration was generally higher in shallow water (200 m), with mean values of 0.364±0.311 µg/L and 0.206±0.192 µg/L respectively. Vertically, the maximum total Chl a concentration appeared at depths of 30-50 m and gradually decreased below 100 m. The size-fractionated Chl a concentrations of grid stations and time-series stations (SEATS and J4) were determined, with values of pico- (0.7-2 µm), nano- (2-20 µm) and micro-plankton (20-200 µm) ranging from 0.001-0.287 (0.093±0.071 µg/L), 0.004-1.149 (0.148±0.192 µg/L) and 0.001-0.208 (0.023±0.036 µg/L), respectively. Phaeopigment concentrations were determined at specific depths at ten stations, except for at station A9, and varied from 0.007 to 0.572 (0.127±0.164) µg/L. Nano-and pico-plankton were the major contributors to total phytoplankton biomass, accounting for 50.99%±15.01% and 39.30%±15.41%, respectively, whereas microplankton only accounted for 9.39%±8.66%. The results indicate that the contributions of microplankton to total Chl a biomass were less important than picoplankton or nanoplankton in the surveyed NSCS. Different sized-Chl a had similar spatial patterns, with peak values all observed in subsurface waters (30-50 m). The summer monsoon, Kuroshio waters, Zhujiang (Pearl) River plume, and hydrological conditions are speculated to be the factors controlling the abundance and spatial heterogeneity of Chl a biomass in the NSCS.

  5. Radiation characteristics of Chlamydomonas reinhardtii CC125 and its truncated chlorophyll antenna transformants tla1, tlaX and tla1-CW{sup +}

    Energy Technology Data Exchange (ETDEWEB)

    Berberoglu, Halil; Pilon, Laurent [Mechanical and Aerospace Engineering Department, Henry Samueli School of Engineering and Applied Science, University of California, Los Angeles, CA 90095 (United States); Melis, Anastasios [Department of Plant and Microbial Biology, University of California, Berkeley, CA 94720 (United States)

    2008-11-15

    This experimental study reports, for the first time, the radiation characteristics of the unicellular green algae Chlamydomonas reinhardtii strain CC125 and its truncated chlorophyll antenna transformants tla1, tlaX and tla1-CW{sup +}. Photobiological hydrogen production is a sustainable alternative to thermo-chemical and electrolytic technologies with the possible advantage of carbon dioxide mitigation. However, scale-up of photobioreactors from bench top to industrial scale is made difficult by excessive absorption and waste of light energy as heat and fluorescence. This results in limited light penetration into the photobioreactor and low solar to hydrogen energy conversion efficiency. To overcome these challenges, the algae C. reinhardtii have been genetically engineered with reduced pigment concentrations in their photosystems. This can improve the performance of photobioreactors by increasing the saturation irradiance of algae and quantum efficiency of photobiological hydrogen production. The extinction and absorption coefficients of all strains studied are obtained from normal-normal and normal-hemispherical transmittance measurements over the spectral range from 300 to 1300 nm. Moreover, a polar nephelometer is used to measure the scattering phase function of the microorganisms at 632.8 nm. It is established that the wild strain C. reinhardtii CC125 has major absorption peaks at 435 and 676 nm, corresponding to the in vivo absorption peaks of chlorophyll a, and at 475 and 650 nm corresponding to those of chlorophyll b. The genetically engineered strains have less chlorophyll pigments than the wild strain and thus have smaller absorption cross-sections. In particular, the mutant tlaX features a significant reduction in chlorophyll b concentration. For all mutants, however, the reduction in the absorption cross-section is accompanied by an increase in scattering cross-section. Although scattering becomes the dominant phenomenon contributing to the overall

  6. The lowest-energy chlorophyll of photosystem II is adjacent to the peripheral antenna: Emitting states of CP47 assigned via circularly polarized luminescence.

    Science.gov (United States)

    Hall, Jeremy; Renger, Thomas; Müh, Frank; Picorel, Rafael; Krausz, Elmars

    2016-09-01

    The identification of low-energy chlorophyll pigments in photosystem II (PSII) is critical to our understanding of the kinetics and mechanism of this important enzyme. We report parallel circular dichroism (CD) and circularly polarized luminescence (CPL) measurements at liquid helium temperatures of the proximal antenna protein CP47. This assembly hosts the lowest-energy chlorophylls in PSII, responsible for the well-known "F695" fluorescence band of thylakoids and PSII core complexes. Our new spectra enable a clear identification of the lowest-energy exciton state of CP47. This state exhibits a small but measurable excitonic delocalization, as predicated by its CD and CPL. Using structure-based simulations incorporating the new spectra, we propose a revised set of site energies for the 16 chlorophylls of CP47. The significant difference from previous analyses is that the lowest-energy pigment is assigned as Chl 612 (alternately numbered Chl 11). The new assignment is readily reconciled with the large number of experimental observations in the literature, while the most common previous assignment for the lowest energy pigment, Chl 627(29), is shown to be inconsistent with CD and CPL results. Chl 612(11) is near the peripheral light-harvesting system in higher plants, in a lumen-exposed region of the thylakoid membrane. The low-energy pigment is also near a recently proposed binding site of the PsbS protein. This result consequently has significant implications for our understanding of the kinetics and regulation of energy transfer in PSII. PMID:27342201

  7. Capacitive top-loading of a mobile phone antenna for size reduction

    DEFF Research Database (Denmark)

    Thaysen, Jesper; Jakobsen, Kaj Bjarne

    2004-01-01

    Capacitive top loading for size reduction of the Planar Inverted F Antenna (PIFA) is presented in this paper. A measured 39% reduction from 1.8 to 1.22 GHz of the resonant frequency is accomplished by using a 1.1 pF distributed capacitor. The simulated –6 dB bandwidth is 9% with a peak radiation...

  8. The size-fractionated chlorophyll a and primary productivity in the Bering Sea during the summer of 2003

    Institute of Scientific and Technical Information of China (English)

    LIU Zilin; CHEN Jianfang; CHEN Zhongyuan; ZHANG Tao; ZHANG Haisheng

    2005-01-01

    Investigations of chlorophyll a and primary productivity were carried out in the Bering Sea along the BR line and the BS line during the Second Chinese National Arctic Research Expedition in the summer of 2003. The results showed that the surface chlorophyll a concentrations were 0.199~1.170 μg/dm3, and the average value was 0.723 μg/dm3 on the BR line. For the BS line, the surface chlorophyll a concentrations were 0.519~4.644 μg/dm3 (average 1.605 μg/dm3) and 0.568~14.968 μg/dm3 (average 5.311 μg/dm3)during the early and late summer, respectively. The average value in the late summer was much higher than that in the early summer.The high values (more than 4.0 μg/dm3) occurred at stations of the BS line in the southern Bering Strait. The chlorophyll a concentrations in the subsurface layer were higher than those in the surface layer. The results of the size-fractionated chlorophyll a showed that the contribution of the picoplankton to total chlorophyll a was the predominance at the early summer and the contribution of the netplankton was the predominance at the late summer. The carbon potential primary productivities varied between 0.471 and 1.147 mg/(m3·h) on the BR line, with average rates of 0.728 mg/(m3·h). The primary productivities on the BS line were much higher than those of the BR line, ranging from 1.227 mg/(m3·h) at the early summer to 19.046 mg/(m3·h) at the late summer. The results of 1.147 mg/(m3·h) on the BR line, with average rates of 0.728 mg/(m3·h). The primary productivities on the BS line were much higher than those of the BR line, ranging from 1.227 mg/(m3·h) at the early summer to 19.046 mg/(m3·h) at the late summer. The results of the size-fractionated primary productivity showed that the contribution of the nanoplankton to total productivity was the predominance at the early summer and the contribution of the netplankton was predominance at the late summer. The assimilation number of photosynthesis was 0.45~2.80 mg

  9. A Size Reduction Technique for Mobile Phone PIFA Antennas Using Lumped Inductors

    DEFF Research Database (Denmark)

    Thaysen, Jesper; Jakobsen, Kaj Bjarne

    2005-01-01

    A size reduction technique for the planar inverted-F antenna (PIFA) is presented. An 18 nH lumped inductor is used in addition to a small 0.3 cm3 PIFA. The PIFA is located on dielectric foam, 5 mm above a 40 mm × 100 mm ground plane. It is possible to reduce the center frequency (|S11|min) by 33...

  10. A Size Reduction Technique for Mobile Phone PIFA Antennas Using Lumped Inductors

    DEFF Research Database (Denmark)

    Thaysen, Jesper; Jakobsen, Kaj Bjarne

    2005-01-01

    A size reduction technique for the planar inverted-F antenna (PIFA) is presented. An 18 nH lumped inductor is used in addition to a small 0.3 cm3 PIFA. The PIFA is located on dielectric foam, 5 mm above a 40 mm × 100 mm ground plane. It is possible to reduce the center frequency (|S11|min) by 33...... percent for a fixed physical size. The measured – 6 dB bandwidth is 6.7 percent with a peak radiation efficiency of 88 percent....

  11. NOVEL SUPER WIDE BAND ANTENNA WITH WLAN/WiMAX BAND REJECTION AND COMPACT SIZE

    Directory of Open Access Journals (Sweden)

    Hadi Baghali

    2014-01-01

    Full Text Available A 25×25×1.6mm3 implementation of a microstrip-fed printed monopole antenna for the future UWB wireless systems application is presented. It has features of possesses band notched function (from 4.88 to 6.07GHz, extremely wide impedance bandwidth (from 2.58 to 18GHz and its compact size. By using a smooth tapering between the semi fractal-shaped patch and the half ellipse-shaped defected ground plane, the wide impedance bandwidth is achieved with ratio bandwidth larger than 6.97:1. Numerical and experimental results are in good agreement and they indicate that the proposed antenna has a measured 2:1 VSWR bandwidth of 149.8%, except the rejected WLAN band.

  12. Photophysical behavior and assignment of the low-energy chlorophyll states in the CP43 proximal antenna protein of higher plant photosystem II.

    Science.gov (United States)

    Hughes, Joseph L; Picorel, Rafael; Seibert, Michael; Krausz, Elmars

    2006-10-10

    We have employed absorption, circular dichroism (CD), and persistent spectral hole-burning measurements at 1.7 K to study the photoconversion properties and exciton coupling of low-energy chlorophylls (Chls) in the CP43 proximal antenna light-harvesting subunit of photosystem II (PSII) isolated from spinach. These approximately 683 nm states act as traps for excitation energy in isolated CP43. They "bleach" at 683 nm upon illumination and photoconvert to a form absorbing in the range approximately 660-680 nm. We present new data that show the changes in the CD spectrum due to the photoconversion process. These changes occur in parallel with those in absorption, providing evidence that the feature undergoing the apparent bleach is a component of a weakly exciton-coupled system. From our photoconversion difference spectra, we assign four states in the Chl long-wavelength region of CP43, two of which are the known trap states and are both highly localized on single Chls. The other two states are associated with weak exciton coupling (maximally approximately 50 cm(-)(1)) to one of these traps. We propose a mechanism for photoconversion that involves Chl-protein hydrogen bonding. New hole-burning data are presented that indicate this mechanism is distinct to that for narrow-band spectral hole burning in CP43. We discuss the photophysical behavior of the Chl trap states in isolated CP43 compared to their behavior in intact PSII preparations. The latter represent a more intact, physiological complex, and we find no clear evidence that they exhibit the photoconversion process reported here. PMID:17014087

  13. Spinach seed quality - potential for combining seed size grading and chlorophyll flourescence sorting

    DEFF Research Database (Denmark)

    Deleuran, Lise Christina; Olesen, Merete Halkjær; Boelt, Birte

    2013-01-01

    Spinach (Spinacia oleracea L.) seed quality is important for subsequent establishment of baby leaf and other spinach products. The indeterminate flowering pattern in spinach produces seeds of different sizes, and consequently a non-uniform seed lot. Sorting seeds based on novel sorting methods mi...

  14. Distribution characteristics of size-fractionated chlorophyll a,primary production and new production in the Laizhou Bay,July 1997

    Institute of Scientific and Technical Information of China (English)

    蔡煜明; 宁修仁; 刘子琳; 刘诚刚

    2002-01-01

    The distributions of chlorophyll a concentration, primary production and new production were observed in the Laizhou Bay of the Bohai Sea in both spring and neap tides during July 1997. The results showed that there were marked features of spatial zonation in the surveyed area, due to the differences between the geographic environment and the hydrological conditions. Chlorophyll a, primary production and new production were all higher in spring tides than that in neap tides in the Laizhou Bay.The highest values of these parameters were encountered in the central regions of the bay. At most stations, chlorophyll a concentrations at the bottom were higher than that at the surface. The results of size-fractionated chlorophyll a and primary production showed that contributions of nano-combining picoplankton (< 20 μm) to total chlorophyll a and primary production were dominant in phytoplankton community biomass and production of the Laizhou Bay. The environmental factors, primary production and new production in the Laizhou Bay are compared with other sea areas.

  15. The distribution feature of size-fractionated chlorophyll a and primary productivity in Prydz Bay and its north sea area during the austral summer

    Institute of Scientific and Technical Information of China (English)

    刘子琳; 陈忠元

    2003-01-01

    The investigation of size-fractionated chlorophyll a and primary productivity were carried out in three longitudinal sections (63°-69°12′S, 70°30′E, 73°E and 75(30′E) at December 18 -26, 1998 and January 12 -18, 1999 in Prydz Bay and its north sea area, Antarctica. The results showed that surface chlorophyll a concentration were 0.16 - 3.99 μg dm -3. The high values of chlorophyll a concentration ( more than 3.5 μg dm -3 ) were in Prydz Bay and in the west Ladies Bank. The average chlorophyll a concentration at sub-surface layer was higher than that at surface layer; its concentration at the deeper layers of 50 m decreased with increasing depth and that at 200 m depth was only 0.01 -0.95 μg dm-3. The results of size-fractionated chlorophyll a showed that the contribution of the netplanktion to total chlorophyll a was 56% , those of the nanoplankton and the picoplankton were 24% and 20% respectively in the surveyed area. The potential primary productivity at the euphotic zone in the surveyed area was 0. 11 - 11.67 mgC m-3 h -1 and average value was 2.00 ±2.80 mgC m-3h-1. The in-situ productivity in the bay and the continental shelf was higher and that in the deep-sea area was lower. The assimilation number of ted primary productivity show that the contribution of the netplanktion to total productivity was 58% , those of the nanoplankton and the picoplankton were 26% and 16% respectively. The cell abundance of phytoplankton was 1. 6 + 103 - 164. 8 + 103 cell dm-3 in the surface water.

  16. Micro-size antenna structure with vertical nanowires for wireless power transmission and communication.

    Science.gov (United States)

    Kang, Jong-Gu; Jeong, Yeri; Shin, Jeong Hee; Choi, Ji-Woong; Sohn, Jung Inn; Cha, Seung Nam; Jang, Jae Eun

    2014-11-01

    For biomedical implanted devices, a wireless power or a signal transmission is essential to protect an infection and to enhance durability. In this study, we present a magnetic induction technique for a power transmission without any wire connection between transmitter (Tx) and receiver (Rx) in a micro scale. Due to a micro size effect of a flat spiral coil, a magnetic inductance is not high. To enhance the magnetic inductance, a three dimensional magnetic core is added to an antenna structure, which is consisted of ZnO nano wires coated by a nickel (Ni) layer. ZnO nano wires easily supply a large effective surface area with a vertical structural effect to the magnetic core structure, which induces a higher magnetic inductance with a ferro-magnetic material Ni. The magnetic induction antenna with the magnetic core shows a high inductance value, a low reflection power and a strong power transmission. The power transmission efficiencies are tested under the air and the water medium are almost the same values, so that the magnetic induction technique is quite proper to body implanted systems. PMID:25958501

  17. Distribution of chroococcoid cyanobacteria and size-fractionated chlorophyll a biomass in the central and southern north sea waters during June/July 1989

    Science.gov (United States)

    Iriarte, Arantza; Purdie, Duncan A.

    The spatial and vertical distribution of phycoerythrin(PE)-containing chroococcoid cyanobacteria and the contribution of the <3 μm size fraction to overall phytoplankton chlorophyll a biomass were investigated in the central and southern North Sea during June and July 1989. PE-containing chroococcoid cyanobacteria cell numbers ranged between 6×10 5 and 4.4×10 7 cells·dm -3 and was typically between 0.5×10 7 and 3×10 7 cells·dm -3, lowest numbers being recorded near the British coast in central North Sea waters. The vertical distribution of these cyanobacteria showed no evidence to suggest a preferential accumulation deep in the euphotic zone. The <3 μm size fraction accounted for 6.6 to 57.5% of the total phytoplankton chlorophyll a biomass (mean 19.7%). In general, the relative significance of the <3 μm size fraction decreased with increasing total chlorophyll a biomass.

  18. Tetraband Small-Size Printed Strip MIMO Antenna for Mobile Handset Application

    Directory of Open Access Journals (Sweden)

    Qinghao Zeng

    2012-01-01

    Full Text Available A compact printed multiple-input multiple-output (MIMO antenna for tetraband (GSM900/1800/1900/UMTS mobile handset application is presented. The proposed MIMO antenna, which consists of two coupled-fed loop antennas with symmetrical configuration, was printed on a 120 * 60 * 0.8 mm3 Fr-4 substrate of relative permittivity of 4.4, loss tangent 0.02. Each element antenna requires only a small area of 22.5 * 25 mm2 on the circuit board. The edge-to-edge spacing between the two elements is only 0.03λ0 of 920 MHz. A slot and a dual-inverted-L-shaped ground branch were added in the ground plane to decrease the mature coupling between the antenna elements. The measured isolation of the proposed antenna is better than 15 dB among the four operating frequency bands. The simulated 3D radiation patterns at 900 MHz and 1900 MHz of both antenna elements show that two loop antennas in general cover complementary space regions with good diversity performance. Detailed antenna impedance matching performance comparisons were done to evaluate the benefit of using different decoupling technology. The envelop correlation coefficient is calculated to represent the diversity performance of the MIMO antenna.

  19. The Response of Phytoplankton Size Spectra and Chlorophyll Biomass to Wind-driven Coastal Upwelling off Northern California During the CoOP-WEST Study.

    Science.gov (United States)

    Wilkerson, F. P.; Dugdale, R. C.; Marchi, A.; Hogue, V.; Lassiter, A.; Lew, K.; Lorenzi, A.

    2002-12-01

    During the WEST (Wind Events and Shelf Transport) summer studies of the coastal upwelling region off Bodega Bay, CA, chlorophyll concentrations consistently reached phytoplankton bloom levels following wind driven upwelling events that resulted in high concentrations of pCO2 and nutrients. In most coastal upwelling areas, upwelled nitrate and high rates of new production lie close to the coast in a distinct plume, and their consequences (a band of enhanced chlorophyll) are propagated seaward far beyond the point where upwelled nutrients have been exhausted. Most likely grazing on advected diatoms results in release of regenerated N (ammonium and urea) that is taken up by the small-sized phytoplankton that out-compete diatoms for ammonium and consequently carry coastal new production offshore in the upper layer current system. However in the WEST study area the growing phytoplankton (showing high rates of new production) and productivity are retained on the shelf, and apparently transported alongshore rather than offshore most of the time. The elevated chlorophyll (reaching over 30 μg/l in June 2000) is made up of mostly larger phytoplankton cells with the diatom Chaetoceros spp. dominating during the bloom events. These cells may be grazed or sink and be carried in sub surface currents and re-entrained in the undercurrent, unlike smaller cells that remain in the upper layer. Surface distributions of chlorophyll and phytoplankton size spectra and fluorescence obtained using a CytoSense flow cytometer will be compared between upwelling spring cruises and a non upwelling winter cruise to the CoOP-WEST study site off Bodega Bay, CA.

  20. CIRCULARLY POLARIZED SLOT ANTENNA WITH COMPACT SIZE FOR WLAN/WIMAX APPLICATION

    Directory of Open Access Journals (Sweden)

    Azim Rezaei Motlagh

    2014-01-01

    Full Text Available In this letter a circle patch that have two slots in ground and patch is presented. The antenna is operated in WLAN/WiMAX at 4.7~6 GHz. The 3dB axial ratio bandwidth is 0.5GHz at 5.3~5.8GHz. Comparison results between measured and simulated of antenna are acceptable.

  1. Energy transfer to low energy chlorophyll species prior to trapping by P700 and subsequent electron transfer.

    Science.gov (United States)

    Klug, D R; Giorgi, L B; Crystall, B; Barber, J; Porter, G

    1989-12-01

    It is found that the two singlet state lifetimes observed in medium sized isolated Photosystem One reaction centres belong to two distinct sets of particles. The nanosecond lifetime is due to PS1 particles in which P700 does not trap excitation energy, and the excitation energy is homogeneously distributed within the antennae of these particles. The spectral features of the picosecond component show that excitation energy in the antenna has become largely concentrated in one or more low energy (red) chlorophyll species within 3.5 ps. Antennae which have become decoupled from P700 also appear to be decoupled from these red "ancillary" chlorophylls, and this suggests that some substructure or level of organisation links them to P700.The rate of quenching of antenna singlet states appears to be independent of the redox state of P700 under the conditions used here, and oxidising P700 does not prevent excitation energy from reaching the red chlorophyll species in the antenna.We find no evidence in the data presented here of a chlorophyll molecule acting as a "metastable" primary acceptor (A0). The lower limit for the detection of such a species in these data is 20% of the optical density of the transient P700 bleach. PMID:24424816

  2. Light-harvesting regulation from leaf to molecule with the emphasis on rapid changes in antenna size.

    Science.gov (United States)

    Xu, Da-Quan; Chen, Yue; Chen, Gen-Yun

    2015-05-01

    In the sunlight-fluctuating environment, plants often encounter both light-deficiency and light-excess cases. Therefore, regulation of light harvesting is absolutely essential for photosynthesis in order to maximize light utilization at low light and avoid photodamage of the photosynthetic apparatus at high light. Plants have developed a series of strategies of light-harvesting regulation during evolution. These strategies include rapid responses such as leaf movement and chloroplast movement, state transitions, and reversible dissociation of some light-harvesting complex of the photosystem II (LHCIIs) from PSII core complexes, and slow acclimation strategies such as changes in the protein abundance of light-harvesting antenna and modifications of leaf morphology, structure, and compositions. This review discusses successively these strategies and focuses on the rapid change in antenna size, namely reversible dissociation of some peripheral light-harvesting antennas (LHCIIs) from PSII core complex. It is involved in protective role and species dependence of the dissociation, differences between the dissociation and state transitions, relationship between the dissociation and thylakoid protein phosphorylation, and possible mechanism for thermal dissipation by the dissociated LHCIIs. PMID:25773873

  3. Parametric Study of a Small Size 5.8 GHz Slotted Patch Antenna

    Directory of Open Access Journals (Sweden)

    Chandra Prakash

    2014-05-01

    Full Text Available This paper presents a design of a coaxially fed microstrip patch antenna (MSPA with multiple slots for applications in BAN (Body Area Networks, PAN (personal area network and WLAN (Wireless Local Area Network at 5.8 GHz. The radiation characteristics and the impedance matching of the proposed antenna are evaluated. The parametric study of slot dimensions and position has been performed to optimize the design for high return loss and increased bandwidth. The maximum achievable bandwidth below -10dB is about 590 MHz with peak gain of 5.47dB. The reflection coefficient S11 of -42dB is obtained at resonating frequency of 5.8 GHz in the Industrial Scientific and Medical band (ISM

  4. 应用于WLAN的小型微带天线%Small-size microstrip antenna for WLAN

    Institute of Scientific and Technical Information of China (English)

    谢征兰; 林文斌; 杨广立

    2014-01-01

    为了满足手机无线局域网(WLAN)通信技术的要求,设计了一个三频段单极子贴片天线,通过2个L形支路产生双频辐射。并用软件对该天线进行仿真优化,实现了2.4 GHz、5.2 GHz和5.8 GHz三频段的同时工作,而且该天线结构简单,由L形贴片组合形成,体积小,所占面积为14.5 mm×16.5 mm。仿真结果表明,该天线的尺寸和性能可以在手机WLAN通信系统得到良好的应用。%In order to meet to the requirements of mobile wireless LAN(WLAN)communication technology,a triple-band monopole patch antenna was designed,which can generate double-frequency radiation by two L-shaped branches. An electromag-netic model of the designed antenna was developed for simulation and optimization. It can works simultaneously in three frequen-cy bands at 2.4 GHz,5.2 GHz and 5.8 GHz. The antenna has a simple structure,which is composed of L-shaped patch,and only occupies an area of 14.5 mm×16.5 mm. The simulation results show that the size and performance is suitable for application of mobile WLAN communication system.

  5. Space-Frame Antenna

    Science.gov (United States)

    Curtis, Steven A.

    2010-01-01

    The space-frame antenna is a conceptual antenna structure that would be lightweight, deployable from compact stowage, and capable of deforming itself to a size, shape, and orientation required for a specific use. The space-frame antenna would be a trusslike structure consisting mostly of a tetrahedral mesh of nodes connected by variable-length struts. The deformation of the antenna to a desired size, shape, and orientation would be effected through coordinated lengthening and shorting of the struts.

  6. Design and Simulation of a Reduced –Size VSAT Antenna With Appreciable Gain

    Directory of Open Access Journals (Sweden)

    Emuoyibofarhe O. J

    2011-12-01

    Full Text Available Information technology has become a very vital tool in the world today. There exist the need for the flow of information between arms of an organization such as banks, hospitals, business sectors and the like. Over the ages, different mechanisms of communication have been developed which include telephone exchange, fax, and radio communication, via TV signals. Satellite communication was developed around 1958 to latter enhance communication strategy (13 using different earth stations made up of very small terminal called VSAT which can transmit to and receive signal from spacecraft satellite via the internet. This paper propose a design of a simulation dish that is very small in size (diameter varying the design parameters using Ka brand frequency. And yet work effectively as the usual dish for internet data transmission.

  7. Chlorophylls - natural solar cells

    CERN Document Server

    Jantschi, Lorentz; Balan, Mugur C; Sestras, Radu E

    2011-01-01

    A molecular modeling study was conducted on a series of six natural occurring chlorophylls. Quantum chemistry calculated orbital energies were used to estimate frequency of transitions between occupied molecular orbital and unoccupied molecular orbital energy levels of chlorophyll molecules in vivo conditions in standard (ASTMG173) environmental conditions. Obtained results are in good agreement with energies necessary to fix the Magnesium atom by chlorophyll molecules and with occurrence of chlorophylls in living vegetal organisms.

  8. Hemispheric ultra-wideband antenna.

    Energy Technology Data Exchange (ETDEWEB)

    Brocato, Robert Wesley

    2006-04-01

    This report begins with a review of reduced size ultra-wideband (UWB) antennas and the peculiar problems that arise when building a UWB antenna. It then gives a description of a new type of UWB antenna that resolves these problems. This antenna, dubbed the hemispheric conical antenna, is similar to a conventional conical antenna in that it uses the same inverted conical conductor over a ground plane, but it also uses a hemispheric dielectric fill in between the conductive cone and the ground plane. The dielectric material creates a fundamentally new antenna which is reduced in size and much more rugged than a standard UWB conical antenna. The creation of finite-difference time domain (FDTD) software tools in spherical coordinates, as described in SAND2004-6577, enabled this technological advance.

  9. Rotary antenna attenuator

    Science.gov (United States)

    Dickinson, R. M.; Hardy, J. C.

    1969-01-01

    Radio frequency attenuator, having negligible insertion loss at minimum attenuation, can be used for making precise antenna gain measurements. It is small in size compared to a rotary-vane attenuator.

  10. Light and Heat Induced Denaturation of Photosystem Ⅱ Core Antenna Complex CP47

    Institute of Scientific and Technical Information of China (English)

    1999-01-01

    Light and heat induced denaturation of CP47, the core antenna complex of photosystem Ⅱ purified from spinach, were investigated using absorption and circular dichroism spectra.Light caused the destruction of chlorophyll a and excitonic interaction of chlorophyll a in CP47, while the protein secondary structure was not apparently changed.Heat induced the destruction of protein secondary structure and excitonic interaction of chlorophyll a, but the chlorophyll a molecule was not damaged.The results suggest that both the chlorophyll a molecular structure and the protein native conformation are necessary for excitonic interaction of chlorophyll a and the energy transfer function of the chlorophyll a binding protein.

  11. Cavity Backed Slot Antenna

    Directory of Open Access Journals (Sweden)

    Sarang Masani, Ila Parmar, Hitendra Jadeja

    2013-05-01

    Full Text Available Among the current driving forces in wireless communications, there is a need for compact, efficient, inexpensive and reproducible antennas. In some instances, particularly long-distance applications, radiators with directive, high-gain characteristics are necessary. This paper proposes a cavity-backed slot antenna to that end. This antenna will enhance the gain, directivity and can also be easily flush mounted to the flying object. The shape and size of the slot can be effectively utilized to get the desired result. The proposed antenna is feed by waveguide which facilitate it to be applicable at high power operation where coaxial cable fails due to skin effect. Present antenna is verified using Numerical Technique called Finite Element Method FEM. The conception of this antenna is realized by the software HFSS “Ansoft-High Frequency Structure Simulator”. By properly selecting shapes, dimensions of the slots and number of slot affects the parameters like return loss, gain along Θ, Ø directions, Cartesian plot and radiation pattern .The Backing of cavity to the slot antenna provide the basics of the gain enhancement and the slot loading effect and the cavity volume plays an important role in achieving the desired return loss at the specific frequency.The simulated antenna shows the 7.0944 db of gain and return loss of -28.60. The proposed antenna works at 6 GHz.

  12. Chlorophyll and starch assays

    OpenAIRE

    sprotocols

    2015-01-01

    Chlorophyll, starch, and sugar contents are good indicators of growth vigor in plants. To measure the chlorophyll content, we used a modified protocol (1,2). The starch content was determined using iodine staining (3) and enzymatic reactions (4-6).

  13. Smart antennas

    CERN Document Server

    Godara, Lal Chand

    2004-01-01

    INTRODUCTION Antenna GainPhased Array AntennaPower Pattern Beam Steering Degree of Freedom Optimal AntennaAdaptive AntennaSmart AntennaSummary NARROWBAND PROCESSINGSignal Model Conventional BeamformerNull Steering BeamformerOptimal BeamformerOptimization Using Reference SignalBeam Space Processing Effect of ErrorsNotation and AbbreviationsReferencesADAPTIVE PROCESSINGSample Matrix Inversion AlgorithmUnconstrained Least Mean Squares AlgorithmNormalized Least Mean Squares AlgorithmConstrained

  14. Strong enhancement of nano-sized circularly polarized light using an aperture antenna with V-groove structures.

    Science.gov (United States)

    Cai, Yongfu; Ikeda, Soushi; Nakagawa, Katsuji; Kikuchi, Hiroshi; Shimidzu, Naoki; Ishibashi, Takayuki

    2015-04-01

    We present a new type of aperture antenna with V-groove structures that are made of Au to enhance strong circularly polarized light (CPL). Simulations using the finite element method revealed that strong CPL was enhanced within the aperture with a diameter of 10 nm. The intensity of the electric field was enhanced and was 22,700 times greater than that of the incident light. The channel plasmon polaritons generated in the V-groove structures were responsible for the strong enhancement. The influence of the angle and length of the V-groove on the enhancement of the CPL was investigated. PMID:25831317

  15. Chlorophyll Degradation in Horticultural Crops

    OpenAIRE

    Kaewsuksaeng, Samak

    2011-01-01

    One of the symptoms of senescence in harvested horticultural crops is the loss of greenness that comes with the degradation of chlorophyll. With senescence, the chlorophyll-degrading enzyme activities such as chlorophyllase, Mg-dechelatase or Mg-dechelation activity, a new chlorophyll-degrading enzyme, pheophytinase, pheophorbidase and chlorophyll-degrading peroxidase, which are involved in chlorophyll degradation, affected greatly in stored horticultural crops. The chlorophyll derivatives, e...

  16. The role of chlorophyll b in photosynthesis: Hypothesis

    Directory of Open Access Journals (Sweden)

    Park Hyoungshin

    2001-10-01

    Full Text Available Abstract Background The physico-chemical properties of chlorophylls b and c have been known for decades. Yet the mechanisms by which these secondary chlorophylls support assembly and accumulation of light-harvesting complexes in vivo have not been resolved. Presentation Biosynthetic modifications that introduce electronegative groups on the periphery of the chlorophyll molecule withdraw electrons from the pyrrole nitrogens and thus reduce their basicity. Consequently, the tendency of the central Mg to form coordination bonds with electron pairs in exogenous ligands, a reflection of its Lewis acid properties, is increased. Our hypothesis states that the stronger coordination bonds between the Mg atom in chlorophyll b and chlorophyll c and amino acid sidechain ligands in chlorophyll a/b- and a/c-binding apoproteins, respectively, enhance their import into the chloroplast and assembly of light-harvesting complexes. Testing Several apoproteins of light-harvesting complexes, in particular, the major protein Lhcb1, are not detectable in leaves of chlorophyll b-less plants. A direct test of the hypothesis – with positive selection – is expression, in mutant plants that synthesize only chlorophyll a, of forms of Lhcb1 in which weak ligands are replaced with stronger Lewis bases. Implications The mechanistic explanation for the effects of deficiencies in chlorophyll b or c points to the need for further research on manipulation of coordination bonds between these chlorophylls and chlorophyll-binding proteins. Understanding these interactions will possibly lead to engineering plants to expand their light-harvesting antenna and ultimately their productivity.

  17. Design and Analysis of a Multiband Koch Fractal Monopole Antenna

    OpenAIRE

    Adam, Ismahayati; Soh, Ping Jack; Hadibah, R; Vandenbosch, Guy

    2011-01-01

    This work presents the design and investigation of the monopole and Koch fractal antenna. The fractal concept and geometry has been used in antenna design to obtain multi-band behavior and miniaturized size, as both of these characteristics are important requirements in current antenna design trends. The aim of this paper is to evaluate the antenna performance between monopole antenna and third iteration Koch fractal antenna. Antenna properties such as reflection coefficient (S11), bandwidth,...

  18. Antenna complexes protect Photosystem I from Photoinhibition

    Directory of Open Access Journals (Sweden)

    Hienerwadel Rainer

    2009-06-01

    Full Text Available Abstract Background Photosystems are composed of two moieties, a reaction center and a peripheral antenna system. In photosynthetic eukaryotes the latter system is composed of proteins belonging to Lhc family. An increasing set of evidences demonstrated how these polypeptides play a relevant physiological function in both light harvesting and photoprotection. Despite the sequence similarity between antenna proteins associated with the two Photosystems, present knowledge on their physiological role is mostly limited to complexes associated to Photosystem II. Results In this work we analyzed the physiological role of Photosystem I antenna system in Arabidopsis thaliana both in vivo and in vitro. Plants depleted in individual antenna polypeptides showed a reduced capacity for photoprotection and an increased production of reactive oxygen species upon high light exposure. In vitro experiments on isolated complexes confirmed that depletion of antenna proteins reduced the resistance of isolated Photosystem I particles to high light and that the antenna is effective in photoprotection only upon the interaction with the core complex. Conclusion We show that antenna proteins play a dual role in Arabidopsis thaliana Photosystem I photoprotection: first, a Photosystem I with an intact antenna system is more resistant to high light because of a reduced production of reactive oxygen species and, second, antenna chlorophyll-proteins are the first target of high light damages. When photoprotection mechanisms become insufficient, the antenna chlorophyll proteins act as fuses: LHCI chlorophylls are degraded while the reaction center photochemical activity is maintained. Differences with respect to photoprotection strategy in Photosystem II, where the reaction center is the first target of photoinhibition, are discussed.

  19. Chlorophyll_Master

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set included chlorophyll for each subregion in the study (Georges Bank, Gulf of Maine, Southern New England, Middle Atlantic Bight) . The data came from...

  20. OSU Chlorophyll Bloom Product

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This product was developed for the Oregon coast based on the observed change between running 8-day composite chlorophyll-a (CHL) data obtained by the MODerate...

  1. Chlorophyll: The wonder pigment

    Digital Repository Service at National Institute of Oceanography (India)

    Bhat, S.R.

    juice or grow our own sprouts, instead we try to get the benefits of green foods through capsules, tablets or powder of dehydrated or freeze dried forms of wheat grass, blue green algae, or different cereal grasses. Chlorophyll or its derivative... vegetables rich in micronutrients are spinach, drum stick leaves, lettuce, cucumber, beans and green peas. SCIENCE REPORTER, July 2005 31 Feature Article Chlorophyll in Algae Amazingly, some freshwater and marine algae, yet to find place in our daily diet...

  2. Optofluidic chlorophyll lasers.

    Science.gov (United States)

    Chen, Yu-Cheng; Chen, Qiushu; Fan, Xudong

    2016-06-21

    Chlorophylls are essential for photosynthesis and also one of the most abundant pigments on earth. Using an optofluidic ring resonator of extremely high Q-factors (>10(7)), we investigated the unique characteristics and underlying mechanism of chlorophyll lasers. Chlorophyll lasers with dual lasing bands at 680 nm and 730 nm were observed for the first time in isolated chlorophyll a (Chla). Particularly, a laser at the 730 nm band was realized in 0.1 mM Chla with a lasing threshold of only 8 μJ mm(-2). Additionally, we observed lasing competition between the two lasing bands. The presence of laser emission at the 680 nm band can lead to quenching or significant reduction of laser emission at the 730 nm band, effectively increasing the lasing threshold for the 730 nm band. Further concentration-dependent studies, along with theoretical analysis, elucidated the mechanism that determines when and why the laser emission band appears at one of the two bands, or concomitantly at both bands. Finally, Chla was exploited as the donor in fluorescence resonance energy transfer to extend the laser emission to the near infrared regime with an unprecedented wavelength shift as large as 380 nm. Our work will open a door to the development of novel biocompatible and biodegradable chlorophyll-based lasers for various applications such as miniaturized tunable coherent light sources and in vitro/in vivo biosensing. It will also provide important insight into the chlorophyll fluorescence and photosynthesis processes inside plants. PMID:27220992

  3. Plasma antennas

    CERN Document Server

    Anderson, Theodore

    2011-01-01

    The plasma antenna is an emerging technology that partially or fully utilizes ionized gas as the conducting medium instead of metal to create an antenna. The key advantages of plasma antennas are that they are highly reconfigurable and can be turned on and off. The disadvantage is that the plasma antennas require energy to be ionized. This unique resource provides you with a solid understanding of the efficient design and prototype development of plasma antennas, helping you to meet the challenge of reducing the power required to ionize the gas at various plasma densities. You also find thorou

  4. Numerical analysis of patch antenna as antenna array element

    OpenAIRE

    Kizimenko, V.; Bobkov, Y

    2009-01-01

    The patch antennas as antenna array element can be modeling by finite element method (programs Microwave Office, Ansoft HFSS and other). But this method need to use fast computer with memory large size. In this work the authors make an attempt to use thin wire integral equation method for patch antenna analysis. The results of modeling by proposed method are compared with the same of modeling by finite elements method and experimental results.

  5. Multiple band circularly polarized microstrip antenna

    Science.gov (United States)

    Yu, I. P. (Inventor)

    1980-01-01

    A multiple antenna assembly for communicating electromagnetic radiation is disclosed. An antenna element stack is constructed of a plurality of elliptical lamina antenna elements mutally separated by layers of dielectric material, and separated from a ground plane by dielectric material. The antenna assembly is coupled through a feed line in contact with the top antenna element. A conductor joins the remaining antenna elements to the ground plane. Each individual antenna element is operable for communication reception and transmission within a frequency band determined by the size of the particular antenna element. The sizes of the antenna elements may be selected to provide electromagnetic radiation communication over several distinct frequency bands, or to connect the individual bands into a broad band.

  6. Logarithmic Slots Antennas Using Substrate Integrated Waveguide

    OpenAIRE

    Jahnavi Kachhia; Amit Patel,; Alpesh Vala; Romil Patel; Keyur Mahant

    2015-01-01

    This paper represents new generation of slotted antennas for satellite application where the loss can be compensated in terms of power or gain of antenna. First option is very crucial because it totally depends on size of satellite so we have proposed the high gain antenna creating number of rectangular, trapezoidal, and I shape slots in logarithm size in Substrate Integrated Waveguide (SIW) structure. The structure consists of an array of various shape slots antenna designed to operate in C ...

  7. A COMPACT CIRCULARLY POLARIZED SLOTTED MICROSTRIP ANTENNA

    OpenAIRE

    V. Jebaraj; K.R.S. Ravi Kumar; D. Mohanageetha

    2014-01-01

    Slot antennas are often used at UHF and microwave frequencies. In slot antenna for RFID reader applications the frequency ranges from 902-923MHz to achieve circular polarization. The shapes and size of the slot, as well as the driving frequency, determine the radiation distribution pattern. The proposed compact size circularly polarized slotted microstrip antenna are summarized with design rules. The circularly polarized radiation in square patch antenna can be obtained by perturbation techni...

  8. Reconfigurable antenna pattern verification

    Science.gov (United States)

    Drexler, Jerome P. (Inventor); Becker, Robert C. (Inventor); Meyers, David W. (Inventor); Muldoon, Kelly P. (Inventor)

    2013-01-01

    A method of verifying programmable antenna configurations is disclosed. The method comprises selecting a desired antenna configuration from a plurality of antenna configuration patterns, with the selected antenna configuration forming at least one reconfigurable antenna from reconfigurable antenna array elements. The method validates the formation of the selected antenna configuration to determine antenna performance of the at least one reconfigurable antenna.

  9. Reconfigurable antennas

    CERN Document Server

    Bernhard, Jennifer

    2007-01-01

    This lecture explores the emerging area of reconfigurable antennas from basic concepts that provide insight into fundamental design approaches to advanced techniques and examples that offer important new capabilities for next-generation applications. Antennas are necessary and critical components of communication and radar systems, but sometimes their inability to adjust to new operating scenarios can limit system performance. Making antennas reconfigurable so that their behavior can adapt with changing system requirements or environmental conditions can ameliorate or eliminate these restricti

  10. Microstrip Antenna

    OpenAIRE

    Anuj Mehta

    2015-01-01

    Abstract This article presents an overview of the microstrip patch antenna and its design techniques. Basically a microstrip patch antenna comprises of a trace of copper or any other metal of any geometry on one side of a standard printed circuit board substrate with other side grounded. The antenna is fed using various feeding techniques like coaxial strip line aperture coupling or proximity coupling techniques. The working principle and the radiation mechanism have also been described. The ...

  11. Lil3 Assembles with Proteins Regulating Chlorophyll Synthesis in Barley.

    Directory of Open Access Journals (Sweden)

    Astrid Mork-Jansson

    Full Text Available The light-harvesting-like (LIL proteins are a family of membrane proteins that share a chlorophyll a/b-binding motif with the major light-harvesting antenna proteins of oxygenic photoautotrophs. LIL proteins have been associated with the regulation of tetrapyrrol biosynthesis, and plant responses to light-stress. Here, it was found in a native PAGE approach that chlorophyllide, and chlorophyllide plus geranylgeraniolpyrophosphate trigger assembly of Lil3 in three chlorine binding fluorescent protein bands, termed F1, F2, and F3. It is shown that light and chlorophyllide trigger accumulation of protochlorophyllide-oxidoreductase, and chlorophyll synthase in band F3. Chlorophyllide and chlorophyll esterified to geranylgeraniol were identified as basis of fluorescence recorded from band F3. A direct interaction between Lil3, CHS and POR was confirmed in a split ubiquitin assay. In the presence of light or chlorophyllide, geranylgeraniolpyrophosphate was shown to trigger a loss of the F3 band and accumulation of Lil3 and geranylgeranyl reductase in F1 and F2. No direct interaction between Lil3 and geranylgeraniolreductase was identified in a split ubiquitin assay; however, accumulation of chlorophyll esterified to phytol in F1 and F2 corroborated the enzymes assembly. Chlorophyll esterified to phytol and the reaction center protein psbD of photosystem II were identified to accumulate together with psb29, and APX in the fluorescent band F2. Data show that Lil3 assembles with proteins regulating chlorophyll synthesis in etioplasts from barley (Hordeum vulgare L..

  12. Pulse amplitude modulated chlorophyll fluorometer

    Energy Technology Data Exchange (ETDEWEB)

    Greenbaum, Elias; Wu, Jie

    2015-12-29

    Chlorophyll fluorometry may be used for detecting toxins in a sample because of changes in micro algae. A portable lab on a chip ("LOAC") based chlorophyll fluorometer may be used for toxin detection and environmental monitoring. In particular, the system may include a microfluidic pulse amplitude modulated ("PAM") chlorophyll fluorometer. The LOAC PAM chlorophyll fluorometer may analyze microalgae and cyanobacteria that grow naturally in source drinking water.

  13. A Compact UWB Diversity Antenna

    Directory of Open Access Journals (Sweden)

    Hui Zhao

    2014-01-01

    Full Text Available A compact printed ultrawideband (UWB diversity antenna with a size of 30 mm × 36 mm operating at a frequency range of 3.1–10.6 GHz is proposed. The antenna is composed of two semielliptical monopoles fed by two microstrip lines. Two semicircular slots, two rectangular slots, and one stub are introduced in the ground plane to adjust the impedance bandwidth of the antenna and improve the isolation between two feeding ports. The simulated and measured results show that impedance bandwidth of the proposed antenna can cover the whole UWB band with a good isolation of < −15 dB. The radiation patterns, peak antenna gain, and envelope correlation coefficient are also measured and discussed. The measured results show that the proposed antenna can be a good candidate for some portable MIMO/diversity UWB applications.

  14. Reconfigurable Monopole Antennas With Circular Polarization

    OpenAIRE

    Panahi, Afshin

    2015-01-01

    This thesis presents research on printed circularly-polarized monopole antennas and their application in reconfigurable monopole antennas. The proposed circularly-polarised monopole antennas benefit from advantages such as small size, low-cost, low-profile and simple designs. The first part of this thesis introduces three printed circularly-polarized monopole antennas for global navigation satellite systems and Wi-Fi applications. The primary focus is on the ground plane which is used as a ra...

  15. As clorofilas The chlorophylls

    Directory of Open Access Journals (Sweden)

    Nivia Maria Streit

    2005-06-01

    Full Text Available As clorofilas são pigmentos verdes, comuns em todas as células fotossintéticas. Por sua estrutura química ser instável, são facilmente degradadas, resultando em produtos de decomposição que modificam a percepção e qualidade dos alimentos. Esta revisão trata dos vários fatores que interferem na degradação das clorofilas, como a luz, radiação, calor, ácidos, oxigênio, alteração enzimática e interação com outros pigmentos. Também, outro aspecto a ser abordado é a utilização das clorofilas como corantes, através da formação de complexos que tornam esses pigmentos mais estáveis à decomposição.The Chlorophylls are a common green pigment to all photosynthetic cells. They are easily degraded, because of their unstable chemical structure. Degradation results in products alter the perception and quality of foods. This review discusses the various factors, that interfere on chlorophyll degradation such as light, irradiation, heat, acids, oxygen, enzymatical alteration and the interaction with other pigments. Also, the other topic that was mentioned the utilization of the chlorophylls as dyes through a complex formation that make this pigment more stable to degradation.

  16. Design of LTCC Based Fractal Antenna

    KAUST Repository

    AdbulGhaffar, Farhan

    2010-09-01

    The thesis presents a Sierpinski Carpet fractal antenna array designed at 24 GHz for automotive radar applications. Miniaturized, high performance and low cost antennas are required for this application. To meet these specifications a fractal array has been designed for the first time on Low Temperature Co-fired Ceramic (LTCC) based substrate. LTCC provides a suitable platform for the development of these antennas due to its properties of vertical stack up and embedded passives. The complete antenna concept involves integration of this fractal antenna array with a Fresnel lens antenna providing a total gain of 15dB which is appropriate for medium range radar applications. The thesis also presents a comparison between the designed fractal antenna and a conventional patch antenna outlining the advantages of fractal antenna over the later one. The fractal antenna has a bandwidth of 1.8 GHz which is 7.5% of the centre frequency (24GHz) as compared to 1.9% of the conventional patch antenna. Furthermore the fractal design exhibits a size reduction of 53% as compared to the patch antenna. In the end a sensitivity analysis is carried out for the fractal antenna design depicting the robustness of the proposed design against the typical LTCC fabrication tolerances.

  17. Cylindrical aggregates of chlorophylls studied by small-angle neutron scatter

    International Nuclear Information System (INIS)

    Neutron small-angle scattering has demonstrated tubular chlorophyll aggregates formed by self-assembly of a variety of chlorophyll types in nonpolar solvents. The size and other properties of the tubular aggregates can be accounted for by stereochemical properties of the chlorophyll molecules. Features of some of the structures are remarkably similar to light harvesting chlorophyll complexes in vivo, particularly for photosynthetic bacteria. These nanotube chlorophyll structures may have applications as light harvesting biomaterials where efficient energy transfer occurs from an excited state which is highly delocalized

  18. Cylindrical aggregates of chlorophylls studied by small-angle neutron scatter

    Energy Technology Data Exchange (ETDEWEB)

    Worcester, D.L. [Univ. of Missouri, Columbus, MO (United States); Katz, J.J. [Argonne National Laboratory, IL (United States)

    1994-12-31

    Neutron small-angle scattering has demonstrated tubular chlorophyll aggregates formed by self-assembly of a variety of chlorophyll types in nonpolar solvents. The size and other properties of the tubular aggregates can be accounted for by stereochemical properties of the chlorophyll molecules. Features of some of the structures are remarkably similar to light harvesting chlorophyll complexes in vivo, particularly for photosynthetic bacteria. These nanotube chlorophyll structures may have applications as light harvesting biomaterials where efficient energy transfer occurs from an excited state which is highly delocalized.

  19. Chlorophyll a + b content and chlorophyll fluorescence in avocado

    Science.gov (United States)

    One Tonnage (T) and one Simmonds (S) avocado tree and four TxS crosses were evaluated for differences in chlorophyll content and maximal quantum yield of photosystem II in sun and shade-type leaves. Total chlorophyll content by area (Chl a+bar) ranged from 981 mg m-2 in TxS240 to 4339 mg m-2 in Simm...

  20. Characterization of a Synechococcus sp. strain PCC 7002 spontaneous mutant strain defective in accumulation of photosystem II core chlorophyll-protein complexes.

    OpenAIRE

    Webb, R.; Punnett, T

    1989-01-01

    Two photosystem II-associated chlorophyll-protein complexes of Synechococcus sp. strain PCC 7002 were identified. Their polypeptide compositions were similar to those of chlorophyll-containing antenna complexes of other cyanobacteria. Strain GT8B did not possess the complex responsible for 695-nm fluorescence and was unable to grow photoautotrophically; hence, this complex is necessary for photosystem II function in vivo.

  1. Planar MIMO Antenna with Slits for WBAN Applications

    OpenAIRE

    Do-Gu Kang; Jinpil Tak; Jaehoon Choi

    2014-01-01

    A planar MIMO antenna with slits for WBAN applications is proposed. The antenna consists of two PIFAs, ground pads, and two slits. By adding ground pads, the antenna size is reduced with improved impedance matching. Through two slits in a ground plane, the isolation characteristic is improved and the resonant frequency can be controlled. To analyze the antenna performance on a human body, the proposed antenna on a human equivalent flat phantom is investigated through simulations. Regardless o...

  2. Dual-Frequency Operation of Bow-Tie Microstrip Antenna

    Institute of Scientific and Technical Information of China (English)

    钟顺时; 张需溥

    2005-01-01

    Characteristics of a single-feed dual-frequency bow-tie microstrip antenna are studied. By using the variation method, simple formulas for resonant frequencies of the bow-tie microstrip antenna are derived. It is shown that the dual-frequency ratio can be controlled easily by choosing the parameters of the antenna. This design gives compact antenna size and simple antenna structure. Experimental results are presented, verifying the validity of the design.

  3. Circularly polarized antennas

    CERN Document Server

    Gao, Steven; Zhu, Fuguo

    2013-01-01

    This book presents a comprehensive insight into the design techniques for different types of CP antenna elements and arrays In this book, the authors address a broad range of topics on circularly polarized (CP) antennas. Firstly, it introduces to the reader basic principles, design techniques and characteristics of various types of CP antennas, such as CP patch antennas, CP helix antennas, quadrifilar helix antennas (QHA), printed quadrifilar helix antennas (PQHA), spiral antenna, CP slot antennas, CP dielectric resonator antennas, loop antennas, crossed dipoles, monopoles and CP horns. Adva

  4. Antenna reconfiguration using metasurfaces

    OpenAIRE

    Zhu, H; Cheung, WSW; Yuk, TI

    2014-01-01

    The paper describes the designs of a frequency-reconfigurable, polarization reconfigurable and pattern reconfigurable antennas using metasurfaces (MS). The frequency-reconfigurable and polarization reconfigurable antennas are composed of a simple circular patch antenna or slot antenna as the source antenna and a circular MS with the same diameter, with both source antenna and MS implemented using planar technology. The pattern reconfigurable antenna is composed of a circular patch antenna as ...

  5. Diamond dipole active antenna

    OpenAIRE

    Bubnov, I. N.; Falkovych, I. S.; Gridin, A. A.; Stanislavsky, A. A.; Reznik, A. P.

    2015-01-01

    Advantages of the diamond dipole antenna as an active antenna are presented. Such an antenna is like an inverted bow-tie antenna, but the former has some advantages over the ordinary bow-tie antenna. It is shown that the diamond dipole antenna may be an effective element of a new antenna array for low-frequency radio astronomy as well as a communication antenna.

  6. Design of Monopole Antenna Based on Fractal Geometry

    OpenAIRE

    Zhao Yuanqing; Qiu Jinghui; Wang Wei

    2014-01-01

    This paper presents a circular disc monopole antenna based on fractal geometry. The antenna is designed to be applied in UWB systems. So it is essential to ensure that the bandwidth of the antenna ranges from 3.1 GHz to 10.6 GHz, that is, IEEE 802.15.3a. However, the proposed antenna has achieved working in the required bandwidth. Compared to the antennas illustrated in most similar literatures, the proposed antenna has a much smaller size, which makes the antenna possible to be integrated wi...

  7. Dissecting the photosystem II light-harvesting antenna

    OpenAIRE

    Andersson, Jenny

    2003-01-01

    In photosynthesis, sunlight is converted into chemical energy that is stored mainly as carbohydrates and supplies basically all life on Earth with energy. In order to efficiently absorb the light energy, plants have developed the outer light harvesting antenna, which is composed of ten different protein subunits (LHC) that bind chlorophyll a and b as well as different carotenoids. In addition to the light harvesting function, the antenna has the capacity to dissipate excess energy as heat (fe...

  8. DUAL BAND MONOPOLE ANTENNA DESIGN

    Directory of Open Access Journals (Sweden)

    P. Jithu

    2013-06-01

    Full Text Available The WLAN and Bluetooth applications become popular in mobile devices, integrating GSM and ISM bands operation in one compact antenna, can reduce the size of mobile devices. Recently, lot many investigations are carried out in designing a dual band antennas with operating frequencies in GSM band and in ISM band for mobile devices. Printed monopoles are under this investigation. In this paper, dual-band printed monopoles are presented to operate at GSM band i.e. 900 MHz and ISM band i.e. 2.4 GHz. We intend to observe the antenna characteristics on the network analyzer and verify the theoretical results with the practical ones.

  9. Chlorophyll d: the puzzle resolved

    DEFF Research Database (Denmark)

    Larkum, Anthony W D; Kühl, Michael

    2005-01-01

    Chlorophyll a (Chl a) has always been regarded as the sole chlorophyll with a role in photochemical conversion in oxygen-evolving phototrophs, whereas chlorophyll d (Chl d), discovered in small quantities in red algae in 1943, was often regarded as an artefact of isolation. Now, as a result of...... discoveries over the past year, it has become clear that Chl d is the major chlorophyll of a free-living and widely distributed cyanobacterium that lives in light environments depleted in visible light and enhanced in infrared radiation. Moreover, Chl d not only has a light-harvesting role but might also...... replace Chl a in the special pair of chlorophylls in both reactions centers of photosynthesis. Udgivelsesdato: 2005-Aug...

  10. Substrate Integrated Waveguide Antenna Applications

    OpenAIRE

    Wu, Liang

    2015-01-01

    The research objective of this thesis is to provide a better solution for signal interference and reduce the size of waveguide antenna. The background investigations of different waveguide fabrication technologies and switch control methods are detailed in the introductory part of this thesis. Several novel substrate integrated waveguide (SIW) antennas for different purpose are demonstrated in the body of the thesis. The designs are mainly divided into two kinds. The first focuses on the ...

  11. Downsizing Antenna Technologies for Mobile and Satellite Communications

    Science.gov (United States)

    Huang, J.; Densmore, A.; Tulintseff, A.; Jamnejad, V.

    1993-01-01

    Due to the increasing and stringent functional requirements (larger capacity, longer distances, etc.) of modern day communication systems, higher antenna gains are generally needed. This higher gain implies larger antenna size and mass which are undesirable to many systems. Consequently, downsizing antenna technology becomes one of the most critical areas for research and development efforts. Techniques to reduce antenna size can be categorized and are briefly discussed.

  12. A COMPACT CIRCULARLY POLARIZED SLOTTED MICROSTRIP ANTENNA

    Directory of Open Access Journals (Sweden)

    V. Jebaraj

    2014-12-01

    Full Text Available Slot antennas are often used at UHF and microwave frequencies. In slot antenna for RFID reader applications the frequency ranges from 902-923MHz to achieve circular polarization. The shapes and size of the slot, as well as the driving frequency, determine the radiation distribution pattern. The proposed compact size circularly polarized slotted microstrip antenna are summarized with design rules. The circularly polarized radiation in square patch antenna can be obtained by perturbation technique with different shapes of slot in the orthogonal direction. A single feed configuration based symmetric slotted microstrip antenna is adapted to realize the compact circularly polarized microstrip antennas. Based on the perimeter, the size of the slot on microstrip slot antenna are studied and compared. The Operating frequency of the antenna is 912MHz that can be tuned by varying the perimeter of the slot while the keeping the circularly polarized radiation unchanged. The schematic and layout are configured by using Advanced Design System (ADS. Return loss, Resonant Frequency, Axial Ratio (AR, and Gain were determined for the proposed system using ADS. A measured 3dB Axial Ratio (AR bandwidth around 6MHz with 16MHz impedance bandwidth has been achieved for the antenna on a RO3004C substrate with dielectric constant 3.38.

  13. UWB planar antenna technology

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    Recent developments of the ultra-wideband(UWB)planar antennas are reviewed,where the progress in UWB plate monopole antennas,UWB printed monopole antennas and the UWB printed slot antennas is introduced and compared.In addition,the UWB printed antennas with the band-notched functions are also presented.

  14. Koch-Fractal Yagi-Uda Antenna

    DEFF Research Database (Denmark)

    Teisbæk, Henrik Bjørn; Jakobsen, Kaj Bjarne

    2009-01-01

    A Yagi-Uda antenna constructed of three Koch fractal elements is presented. Simulated and measured characteristics of the antenna shows a half-power beam-width of 64◦ achieved with dimensions below a third of a wavelength. Furthermore, the Koch dipole and its size miniaturization capabilities are...

  15. A Compact Diversity Antenna for Handheld Terminals

    Institute of Scientific and Technical Information of China (English)

    Hai-Lin Xiao; Zai-Ping Nie; Yu-Jing Wu

    2009-01-01

    The handheld terminals antenna should have a small size, sufficient gain and big bandwidth. In this paper, a compact planar inverted-L diversity antenna for handheld terminals is proposed. Three diversity antennas operating at 2.15 GHz are designed and the effect of important parameters of the proposed antenna is measured. The isolation is found to be better than 13 dB, the usable bandwidth is about 13%. Moreover, the measured radiation patterns are also obtained that the backward radiation is decreased.

  16. Novel Electrically Small Spherical Electric Dipole Antenna

    DEFF Research Database (Denmark)

    Kim, Oleksiy S.

    2010-01-01

    This paper introduces a novel electrically small spherical meander antenna. Horizontal sections of the meander are composed of wire loops, radii of which are chosen so that the whole structure is conformal to a sphere of radius a. To form the meander the loops are connected by wires at a meridian...... plane. The antenna operates as an electric dipole, i.e. it radiates the TM10 spherical mode. The antenna is self-resonant and can be matched to a wide range of input feed lines without an external matching network. In this paper, a spherical meander antenna of the size ka = 0.27 and the input impedance...

  17. Astigmatism in reflector antennas.

    Science.gov (United States)

    Cogdell, J. R.; Davis, J. H.

    1973-01-01

    Astigmatic phase error in large parabolic reflector antennas is discussed. A procedure for focusing an antenna and diagnosing the presence and degree of astigmatism is described. Theoretical analysis is conducted to determine the nature of this error in such antennas.

  18. A directive pulse antenna

    OpenAIRE

    Titov, A.N.; Titov, A. A.

    2003-01-01

    Using quite general concepts as guidance in the design of an antenna for short pulse transmission and reception, a new type of horn-antenna has been devised. A certain variety of experimental data obtained by the antenna are presented.

  19. Design of Monopole Antenna Based on Fractal Geometry

    Directory of Open Access Journals (Sweden)

    Zhao Yuanqing

    2014-01-01

    Full Text Available This paper presents a circular disc monopole antenna based on fractal geometry. The antenna is designed to be applied in UWB systems. So it is essential to ensure that the bandwidth of the antenna ranges from 3.1 GHz to 10.6 GHz, that is, IEEE 802.15.3a. However, the proposed antenna has achieved working in the required bandwidth. Compared to the antennas illustrated in most similar literatures, the proposed antenna has a much smaller size, which makes the antenna possible to be integrated with portable devices. Firstly, the antenna was designed through CST Microwave Studio. Then, the antenna was fabricated according to the simulated results. At last, the comparison between the simulated results and measured results was carried out which demonstrated good consistency.

  20. Optical antennas and plasmonics

    OpenAIRE

    Park, Q-Han

    2009-01-01

    Optical antenna is a nanoscale miniaturization of radio or microwave antennas that is also governed by the rule of plasmonics. We introduce various types of optical antenna and make an overview of recent developments in optical antenna research. The role of local and surface plasmons in optical antenna is explained through antenna resonance and resonance conditions for specific metal structures are explicitly obtained. Strong electric field is shown to exist within a highly localized region o...

  1. Advanced microwave radiometer antenna system study

    Science.gov (United States)

    Kummer, W. H.; Villeneuve, A. T.; Seaton, A. F.

    1976-01-01

    The practicability of a multi-frequency antenna for spaceborne microwave radiometers was considered in detail. The program consisted of a comparative study of various antenna systems, both mechanically and electronically scanned, in relation to specified design goals and desired system performance. The study involved several distinct tasks: definition of candidate antennas that are lightweight and that, at the specified frequencies of 5, 10, 18, 22, and 36 GHz, can provide conical scanning, dual linear polarization, and simultaneous multiple frequency operation; examination of various feed systems and phase-shifting techniques; detailed analysis of several key performance parameters such as beam efficiency, sidelobe level, and antenna beam footprint size; and conception of an antenna/feed system that could meet the design goals. Candidate antennas examined include phased arrays, lenses, and optical reflector systems. Mechanical, electrical, and performance characteristics of the various systems were tabulated for ease of comparison.

  2. Mutual Coupling Between Two Identical Planar Inverted-F Antennas

    DEFF Research Database (Denmark)

    Thaysen, Jesper

    2002-01-01

    The planar inverted-F antenna (PIFA) is widely used for cellular telephones due to its compactness and size. The objective of this paper is to present the results of numerical investigations of the coupling between two equal PIFA antennas. To analyse the antenna, the method of moment computer...

  3. Antennas in inhomogeneous media

    CERN Document Server

    Galejs, Janis; Fock, V A; Wait, J R

    2013-01-01

    Antennas in Inhomogeneous Media details the methods of analyzing antennas in such inhomogeneous media. The title covers the complex geometrical configurations along with its variational formulations. The coverage of the text includes various conditions the antennas are subjected to, such as antennas in the interface between two media; antennas in compressible isotropic plasma; and linear antennas in a magnetoionic medium. The selection also covers insulated loops in lossy media; slot antennas with a stratified dielectric or isotropic plasma layers; and cavity-backed slot antennas. The book wil

  4. Terminal Antenna Design

    OpenAIRE

    Skrivervik, A. K.; Zurcher, J. F.

    2008-01-01

    This paper introduces first some general considerations about antenna miniaturization and multi-band terminal antenna design. These general design principles are then illustrated on some practical applications.

  5. Magnetic antenna excitation of whistler modes. IV. Receiving antennas and reciprocity

    International Nuclear Information System (INIS)

    Antenna radiation patterns are an important property of antennas. Reciprocity holds in free space and the radiation patterns for exciting and receiving antennas are the same. In anisotropic plasmas, radiation patterns are complicated by the fact that group and phase velocities differ and certain wave properties like helicity depend on the direction of wave propagation with respect to the background magnetic field B0. Interference and wave focusing effects are different than in free space. Reciprocity does not necessarily hold in a magnetized plasma. The present work considers the properties of various magnetic antennas used for receiving whistler modes. It is based on experimental data from exciting low frequency whistler modes in a large uniform laboratory plasma. By superposition of linear waves from different antennas, the radiation patterns of antenna arrays are derived. Plane waves are generated and used to determine receiving radiation patterns of different receiving antennas. Antenna arrays have radiation patterns with narrow lobes, whose angular position can be varied by physical rotation or electronic phase shifting. Reciprocity applies to broadside antenna arrays but not to end fire arrays which can have asymmetric lobes with respect to B0. The effect of a relative motion between an antenna and the plasma has been modeled by the propagation of a short wave packet moving along a linear antenna array. An antenna moving across B0 has a radiation pattern characterized by an oscillatory “whistler wing.” A receiving antenna in motion can detect any plane wave within the group velocity resonance cone. The radiation pattern also depends on loop size relative to the wavelength. Motional effects prevent reciprocity. The concept of the radiation pattern loses its significance for wave packets since the received signal does not only depend on the antenna but also on the properties of the wave packet. The present results are of fundamental interest and of

  6. The molecular photophysics of chlorophyl : a study of its triplet state

    NARCIS (Netherlands)

    Kleibeuker, J.F.

    1977-01-01

    The lowest excited triplet state T size="-1">0 of chlorophyll a , chlorophyll b , bacteriochlorophyll and corresponding pheophytins has been studied by magnetic resonance and optical spectroscopy. Zero field splitting (US) parameters D and E, populating rates, a

  7. Controlling spontaneous emission with plasmonic optical patch antennas

    OpenAIRE

    Belacel, C.; Habert, B.; Bigourdan, F.; Marquier, F.; Hugonin, J.-P.; Michaelis de Vasconcellos, S.; Lafosse, X.; Coolen, L; Schwob, C.; Javaux, C; Dubertret, B.; Greffet, J. -J.; Senellart, P.; Maitre, A.

    2012-01-01

    We experimentally demonstrate the control of the spontaneous emission rate and the radiation pattern of colloidal quantum dots deterministically positioned in a plasmonic patch antenna. The antenna consists of a thin gold microdisk 30 nm above a thick gold layer. The emitters are shown to radiate through the entire patch antenna in a highly directional and vertical radiation pattern. Strong acceleration of spontaneous emission is observed, depending of the antenna size. Considering the double...

  8. CPW-Fed Slot Antenna for Wideband Applications

    OpenAIRE

    Shanmuganantham, T.; K. Balamanikandan; Raghavan, S

    2008-01-01

    A new coplanar waveguide (CPW)-fed wideband printed slot antenna is presented, and the impedance characteristics of this antenna with different sizes of tapers are discussed. The effect of tapering angle with the resonant frequency is also observed. The fundamental parameters of the antenna such as bandwidth, return loss, gain, radiation pattern, and polarization are obtained. All meets the acceptable antenna standards. The measured input impedance bandwidth (return loss < −10 dB) of the pro...

  9. Indian Ocean Dipole and El Nino/Southern Oscillation impacts on regional chlorophyll anomalies in the Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Currie, J.C.; Lengaigne, M.; Vialard, J.; Kaplan, D.M.; Aumont, O.; Naqvi, S.W.A.; Maury, O.

    in the supplemen- tary material of Aumont and Bopp (2006). The biogeochem- ical model has 24 compartments, which include two sizes of sinking particles and four “living” biological pools, rep- resented by two phytoplankton (nano-phytoplankton and di- atoms) and two... model levels. Chlorophyll concentrations were calculated as the sum of chlorophyll from the two phytoplankton size classes (di- atoms and nano-phytoplankton). Surface chlorophyll con- centrations (denoted by SChl; units of mg m−3) were aver- aged over...

  10. On the efficiency of frequency reconfigurable high-Q antennas for 4G standards

    DEFF Research Database (Denmark)

    Barrio, Samantha Caporal Del; Pelosi, Mauro; Pedersen, Gert Frølund

    2012-01-01

    In the actual context of reducing antenna size and operating in multiple bands tunable antennas are investigated. Moreover, high-Q and low-Q tunable antennas are compared with respect to their efficiency. The loss issue that tunable high-Q antennas present is addressed. Using a variable capacitor...

  11. Chlorophylls, Symmetry, Chirality, and Photosynthesis

    Directory of Open Access Journals (Sweden)

    Mathias O. Senge

    2014-09-01

    Full Text Available Chlorophylls are a fundamental class of tetrapyrroles and function as the central reaction center, accessory and photoprotective pigments in photosynthesis. Their unique individual photochemical properties are a consequence of the tetrapyrrole macrocycle, the structural chemistry and coordination behavior of the phytochlorin system, and specific substituent pattern. They achieve their full potential in solar energy conversion by working in concert in highly complex, supramolecular structures such as the reaction centers and light-harvesting complexes of photobiology. The biochemical function of these structures depends on the controlled interplay of structural and functional principles of the apoprotein and pigment cofactors. Chlorophylls and bacteriochlorophylls are optically active molecules with several chiral centers, which are necessary for their natural biological function and the assembly of their supramolecular complexes. However, in many cases the exact role of chromophore stereochemistry in the biological context is unknown. This review gives an overview of chlorophyll research in terms of basic function, biosynthesis and their functional and structural role in photosynthesis. It highlights aspects of chirality and symmetry of chlorophylls to elicit further interest in their role in nature.

  12. Chlorophylls, Symmetry, Chirality, and Photosynthesis.

    OpenAIRE

    Mathias O. Senge; Aoife A. Ryan; Kristie A. Letchford; Stuart A. MacGowan; Tamara Mielke

    2014-01-01

    Chlorophylls are a fundamental class of tetrapyrroles and function as the central reaction center, accessory and photoprotective pigments in photosynthesis. Their unique individual photochemical properties are a consequence of the tetrapyrrole macrocycle, the structural chemistry and coordination behavior of the phytochlorin system, and specific substituent pattern. They achieve their full potential in solar energy conversion by working in concert in highly complex, supramolecular structures ...

  13. Miniaturization of UWB Antennas on Organic Material

    Directory of Open Access Journals (Sweden)

    Symeon Nikolaou

    2016-01-01

    Full Text Available Three planar, CPW-fed, UWB antennas with increasingly reduced size are presented and the miniaturization method is discussed. The first antenna is a CPW-fed elliptical slot with an uneven U-shaped tuning stub, the second antenna is a cactus shaped monopole, and the third one is a miniaturized version of the cactus shaped monopole antenna. All presented antennas have a simulated and measured return loss below −10 dB over the 3.1 to 10.6 GHz UWB frequency range and mostly omnidirectional radiation patterns. The proposed antennas are fabricated on liquid crystal polymer (LCP. The CPW-fed slot antenna requires an overall board dimension of 38 mm × 40 mm, and the evolved cactus monopole is confined in a 28 mm × 32 mm board, while the final miniaturized cactus monopole is printed on 28 mm × 20 mm board, resulting in a 41% and 63% size reduction, respectively. Using both simulations and measurements, the paper analyzes the response of all three antennas and discusses and demonstrates the effectiveness of the implemented miniaturization method.

  14. A True Metasurface Antenna

    OpenAIRE

    Mohamed El Badawe; Almoneef, Thamer S.; Omar M. Ramahi

    2016-01-01

    We present a true metasurface antenna based on electrically-small resonators. The resonators are placed on a flat surface and connected to one feed point using corporate feed. Unlike conventional array antennas where the distance between adjacent antennas is half wavelength to reduce mutual coupling between adjacent antennas, here the distance between the radiating elements is electrically very small to affect good impedance matching of each resonator to its feed. A metasurface antenna measur...

  15. Antenna systems research

    OpenAIRE

    Keen, Keith Malcolm

    1999-01-01

    This thesis is an overview of a number of investigations on antenna systems and related subjects over a period of 28 years, which has resulted in 44 publications in the technical literature, one current patent, and an M.Sc. thesis. The investigations have been grouped into 7 categories: - Log periodic antennas, - Antenna performance measurement techniques, - Spacecraft Antenna Systems, - Satcom Terminal Antennas, - Transmission lines and baluns, - High Radar Cross Secti...

  16. Tri-band small monopole antenna based on SRR units

    Science.gov (United States)

    Shehata, Gehan; Mohanna, Mahmoud; Rabeh, Mohammed Lotfy

    2015-12-01

    In this paper a novel design for a tri-band monopole antenna coupled with metamaterial units is introduced. The proposed antenna was designed to cover WiMAX (2.5, 3.5) and WLAN (5.2) bands. In our proposal, a coplanar waveguide (CPW) fed circular-disk monopole antenna is coupled with three split ring resonator (SRR) units which exist on its back side. In our design a monopole antenna and SRR units are designed first to resonate at 5.2 GHz and 2.5 GHz respectively. In addition, antenna is loaded with post to force resonance at 3.5 GHz. SRR units are used for 2.5 GHz resonance to miniaturize antenna size, and our proposed antenna considered an electrically small antenna (ESA) at its first resonance frequency. Simulated and measured results exhibit a good agreement that validate our design.

  17. ARCHITECTURE OF A CHARGE-TRANSFER STATE REGULATING LIGHT HARVESTING IN A PLANT ANTENNA PROTEIN

    Energy Technology Data Exchange (ETDEWEB)

    Fleming, Graham; Ahn, Tae Kyu; Avenson, Thomas J.; Ballottari, Matteo; Cheng, Yuan-Chung; Niyogi, Krishna K.; Bassi, Roberto; Fleming, Graham R.

    2008-04-02

    Energy-dependent quenching of excess absorbed light energy (qE) is a vital mechanism for regulating photosynthetic light harvesting in higher plants. All of the physiological characteristics of qE have been positively correlated with charge-transfer between coupled chlorophyll and zeaxanthin molecules in the light-harvesting antenna of photosystem II (PSII). In this work, we present evidence for charge-transfer quenching in all three of the individual minor antenna complexes of PSII (CP29, CP26, and CP24), and we conclude that charge-transfer quenching in CP29 involves a de-localized state of an excitonically coupled chlorophyll dimer. We propose that reversible conformational changes in CP29 can `tune? the electronic coupling between the chlorophylls in this dimer, thereby modulating the energy of the chlorophylls-zeaxanthin charge-transfer state and switching on and off the charge-transfer quenching during qE.

  18. Plasma antennas: dynamically configurable antennas for communications

    International Nuclear Information System (INIS)

    In recent years, the rapid growth in both communications and radar systems has led to a concomitant growth in the possible applications and requirements of antennas. These new requirements include compactness and conformality, rapid reconfigurability for directionality and frequency agility. For military applications, antennas should also allow low absolute or out-of-band radar cross-section and facilitate low probability of intercept communications. Investigations have recently begun worldwide on the use of ionised gases or plasmas as the conducting medium in antennas that could satisfy these requirements. Such plasma antennas may even offer a viable alternative to metal in existing applications when overall technical requirements are considered. A recent patent for ground penetrating radar claims the invention of a plasma antenna for the transmission of pulses shorter than 100 ns in which it is claimed that current ringing is avoided and signal processing simplified compared with a metal antenna. A recent US ONR tender has been issued for the design and construction of a compact and rapidly reconfigurable antenna for dynamic signal reception over the frequency range 1 - 45 GHz based on plasma antennas. Recent basic physics experiments at ANU have demonstrated that plasma antennas can attain adequate efficiency, predictable radiation patterns and low base-band noise for HF and VHF communications. In this paper we describe the theory of the low frequency plasma antenna and present a few experimental results

  19. Two Types of Compact UHF Antennas for Partial Discharge Measurement

    Institute of Scientific and Technical Information of China (English)

    JIN Zhuo-rui; SUN Cai-xin; CHENG Chang-kui; LI Jian

    2008-01-01

    To investigate the partial discharge (PD) online monitoring of transformers by ultra-high-frequency (UHF) approaches, high-qualified UHF antennas are focused on as one key technique. The size of UHF sensor used for PD UHF online monitoring in transformer is excessively large, therefore, it is not convenient for internal installation of transformer. Two types of compact UHF antennas with small sizes, a Hilbert fractal antenna and a small loop antenna are presented. PD experiments of three typically artificial insulation defects are executed and both antennas are used for PD measurement. The spectra of power via frequency of detected PD signals are analyzed and compared. The experimental results show that the Hilbert fractal antenna and small loop antenna are qualified for PD online UHF monitoring.

  20. Effect of Phosphatidylcholine on the Steady State Fluorescence of Chlorophyll in Photosystem Ⅱ Particles

    Institute of Scientific and Technical Information of China (English)

    1999-01-01

    Phosphatidylcholine (PC) accounts for less than 1% of the total lipids in plant photosystem II (PSII) particles.In this experiment, PSII particles were reconstituted with PC to construct PSII-PC vesicles.The effect of PC on the steady state fluorescence of chlorophyll (Chl) in PSII particles was studied.The results show that PC significantly affected the fluorescence intensity, but did not obviously affect the fluorescence emission band peak position.PC also did not obviously affect the absorbance at 436 nm or the amide I band peak position in FT-IR spectroscopy of PSII particles.The results suggest that PC may affect the light energy transfer from the antenna chlorophyll molecules to the reaction center chlorophyll molecule (P680).

  1. The chlorophyll-binding protein CP47 in photosystem II. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Vermaas, W.F.J.

    1995-12-31

    Generally, light-harvesting chlorophyll-binding proteins (LHCP) of the Cab family that are prevalent antenna systems in plants are thought to be absent in cyanobacteria. Therefore, it often is tacitly assumed that in cyanobacteria all chlorophyll is associated with the PS II and PS I core antenna. For this reason, it was of interest to investigate what the effect would be of genetic deletion of both the PS I core complex and the PS II core antenna in Synechocystis. Therefore, a mutant was made in which the psaAB genes for the PS I core were deleted, in addition to deletion or inactivation of psbB and/or psbC (coding for CP43). In this series of mutants, also apcE was deleted. In the absence of both CP47 and CP43, also the PS II reaction center proteins D1 and D2 were not detectable in the thylakoid membrane. Thus, both PS II and PS I were deleted in the resulting strains. Nonetheless, a significant amount of chlorophyll (about 15% of that present when PS II was left intact) was found to remain in the PS I-less, psbB{sup {minus}}, psbC{sup {minus}}, apcE{sup {minus}} mutant. This chlorophyll had fluorescence characteristics resembling those of LHC II in higher plants, with a 678 nm emission maximum at 77 K. The properties of this chlorophyll remaining in the absence of PS II and PS I in Synechocystis did not resemble those of chlorophyll bound to a CP43-like protein that has been found in cyanobacteria and that is expressed under iron-stress conditions. However, some similarities in terms of fluorescence emission were observed with the isolated 22 kDa protein encoded by psbS. The role and association of the remaining chlorophyll in the PS I-less, psbB{sup {minus}}, psbC{sup {minus}}, apcE{sup {minus}} mutant remains unclear, however, this chlorophyll protein is expected to be functionally connected to PS II when this photosystem is present.

  2. DESIGN OF PIFA ANTENNA FOR MEDICAL APPLICATIONS

    Directory of Open Access Journals (Sweden)

    A.Umamakeswari

    2013-02-01

    Full Text Available The emerging techniques in the medical field include the use of bio implantable antennas to diagnose the diseases. The major disadvantage of these techniques is the side-effects caused by the radiations in the human body. There have been a lot of advancements in this area to reduce the radiation emitted. One among them is the use of PIFA antenna inside an indestructible capsule (Polyetheretherketones which is helpful in both short and long range communications. The workincludes the design of PIFA antenna using IE3D and MATLAB software. The characteristics of the antenna are analyzed with the aim to reduce the size and radiation effect of antenna and to increase thegain, efficiency and data rate.

  3. Xanthophyll cycle-dependent quenching of photosystem II chlorophyll a fluorescence: formation of a quenching complex with a short fluorescence lifetime.

    OpenAIRE

    Gilmore, A M; Hazlett, T. L.; Govindjee

    1995-01-01

    Excess light triggers protective nonradiative dissipation of excitation energy in photosystem II through the formation of a trans-thylakoid pH gradient that in turn stimulates formation of zeaxanthin and antheraxanthin. These xanthophylls when combined with protonation of antenna pigment-protein complexes may increase nonradiative dissipation and, thus, quench chlorophyll a fluorescence. Here we measured, in parallel, the chlorophyll a fluorescence lifetime and intensity to understand the mec...

  4. Task three: Report: STDN Antenna and preamplifier cost tradeoff study. [combinations of antennas and preamplifiers for several communication environments

    Science.gov (United States)

    1973-01-01

    The general goal of this task, STDN Antenna and Preamplifier G/T Study, was to determine cost-effective combinations of antennas and preamplifiers for several sets of conditions for frequency, antenna elevation angle, and rain. The output of the study includes design curves and tables which indicate the best choice of antenna size and preamplifier type to provide a given G/T performance. The report indicates how to evaluate the cost effectiveness of proposed improvements to a given station. Certain parametric variations are presented to emphasize the improvement available by reducing RF losses and improving the antenna feed.

  5. Compact Triple Band Slotted Microstrip Patch Antenna

    Directory of Open Access Journals (Sweden)

    Ram Singh Kushwaha

    2012-03-01

    Full Text Available This paper presents a compact triple band slot microstrip patch antenna for 1.7/2.92 GHz WLAN applications. The radiating element of the proposed antenna consists of Swastika symbol slot operating at 1.8 GHz, 2.09 GHz, and 2.92 GHz bands. The antenna size is very compact (50 mm x 50 mm x 1.6 mm and covers 1.8 GHz to 2.92 GHz and can be used for AMPS, GSM and WLAN applications. The antenna is fed from a single 50 Ω coaxial cable. Using IE3D software package of Zeland, according to the set size, the antenna is simulated. The composite effect of integrating these techniques and by introducing the novel slotted patch offers a low profile, wide bandwidth, high gain and compact antenna element. The computer simulation results show that the antenna can realize wide band characters with each band having good impedance bandwidth (VSWR ≤ 2 for all the three resonant frequencies.

  6. General properties of dielectric optical antennas.

    Science.gov (United States)

    Schuller, Jon A; Brongersma, Mark L

    2009-12-21

    Using Mie theory we derive a number of general results concerning the resonances of spherical and cylindrical dielectric antennas. Specifically, we prove that the peak scattering cross-section of radiation-limited antennas depends only on the resonance frequency and thus is independent of refractive index and size, a result which is valid even when the resonator is atomic-scale. Furthermore, we derive scaling limits for the bandwidth of dielectric antennas and describe a cylindrical mode which is unique in its ability to support extremely large bandwidths even when the particle size is deeply subwavelength. Finally, we show that higher Q antennas may couple more efficiently to an external load, but the optimal absorption cross-section depends only on the resonance frequency. PMID:20052120

  7. The spherical helical antenna

    OpenAIRE

    Cardoso, J. Christopher

    1992-01-01

    The spherical helical antenna is investigated as a new variation of the conventional helical antenna. The spherical helix is a wire antenna in a helix shape that is wound over a spherical surface instead of the standard cylindrical one. Analysis of this structure requires numerical methods and experimental measurements because its complex geometry makes it very difficult to develop analytic expressions for its radiation characteristics. The wire antenna code ESP, based on the method of ...

  8. Wide Coverage Antennas

    OpenAIRE

    Zackrisson, Jan

    2007-01-01

    Small satellites require small and lightweight antennas for telemetry and command function as well as for downlinking of data. We have during the last thirty years developed a large suite of wide coverage antennas. The basic radiator designs used are quadrifilar helices, waveguides, horns and patch excited cups (PEC) depending on frequency range, coverage requirements and application. The antenna designs range from L-band up to Ka-band frequencies. Typical coverages for the antennas are from ...

  9. Broadband high efficiency active integrated antenna

    OpenAIRE

    Qin, Yi

    2007-01-01

    Active integrated antenna (MA) is a very popular topic of research during recent decades. This is mostly due to its advantages, such as compact size, multiple functions and low cost, etc. The MA system can be regarded as an active microwave circuit which the output or input port is free space instead of a conventional 50-ohm interface. The major drawbacks of the conventional MA include narrow bandwidth, low efficiency, etc. An experimental investigation on broadband slot-coupled antenna is ca...

  10. Circularly Polarized Broadband RFID Microstrip Tag Antenna

    OpenAIRE

    B. Rajini; G. V. Subrahmanyam

    2014-01-01

    In recent years, the application of radio frequency identification (RFID) operating in the ultra-high frequency (UHF) band (860-960MHz) are expanding exponentially, due to the advantages such as long reading distance, high data transfer rate, and small tag size. So the design of a CP tag antenna with broadband characteristic is presently one of the most challenging topics. This project presents a square patch passive RFID tag antenna designed for UHF band. To a...

  11. Evolutionary Optimization of a Quadrifilar Helical Antenna

    Science.gov (United States)

    Lohn, Jason D.; Kraus, William F.; Linden, Derek S.; Clancy, Daniel (Technical Monitor)

    2002-01-01

    Automated antenna synthesis via evolutionary design has recently garnered much attention in the research literature. Evolutionary algorithms show promise because, among search algorithms, they are able to effectively search large, unknown design spaces. NASA's Mars Odyssey spacecraft is due to reach final Martian orbit insertion in January, 2002. Onboard the spacecraft is a quadrifilar helical antenna that provides telecommunications in the UHF band with landed assets, such as robotic rovers. Each helix is driven by the same signal which is phase-delayed in 90 deg increments. A small ground plane is provided at the base. It is designed to operate in the frequency band of 400-438 MHz. Based on encouraging previous results in automated antenna design using evolutionary search, we wanted to see whether such techniques could improve upon Mars Odyssey antenna design. Specifically, a co-evolutionary genetic algorithm is applied to optimize the gain and size of the quadrifilar helical antenna. The optimization was performed in-situ in the presence of a neighboring spacecraft structure. On the spacecraft, a large aluminum fuel tank is adjacent to the antenna. Since this fuel tank can dramatically affect the antenna's performance, we leave it to the evolutionary process to see if it can exploit the fuel tank's properties advantageously. Optimizing in the presence of surrounding structures would be quite difficult for human antenna designers, and thus the actual antenna was designed for free space (with a small ground plane). In fact, when flying on the spacecraft, surrounding structures that are moveable (e.g., solar panels) may be moved during the mission in order to improve the antenna's performance.

  12. A Miniaturization Technique of a Compact Omnidirectional Antenna

    Directory of Open Access Journals (Sweden)

    C. Delaveaud

    2009-12-01

    Full Text Available This paper discusses a miniaturization technique of a compact omnidirectional antenna. A slot loading technique is applied to a well-known low-profile antenna structure whose radiation characteristics are similar to equivalent monopole ones. An equivalent circuit which models the antenna input impedance including the slot effect is also developed in order to illustrate the antenna working principle. The typical dimensions (width x height of the obtained antenna are λ0/11 x λ0/75 (λ0 is the free space operating wavelength which makes it a miniature antenna that can be integrated inside small wireless sensor nodes using narrow band communication systems. Its performances are in accordance with classical fundamental limits, the operating bandwidth and efficiency are significantly reduced with the antenna size reduction.

  13. A deployable 4-meter 180 to 680 GHz antenna for the Scanning Microwave Limb Sounder Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Build and test a full size (4x2 meter aperture) breadboard antenna for SMLS. Demonstrate critical azimuth scanning capability of a 4m SMLS antenna and its...

  14. The mathematical model of antenna and antenna-radome system

    OpenAIRE

    Knyazeva, L. V.; Artishev, A. I.

    2003-01-01

    Methods, algorithms and programs for calculation by computer of the characteristics of the antenna and the antenna-radome system (ARS) are developed. The type of antenna considered is the phased antenna array (PAA) or the cophase antenna with a mechanical beam control (an antenna array - AA). Radome shape is spherical, quasi-conic or flattened ellipsoid. Radome shell is multilayer ( N≥1), same-thickness, or special profile. Errors in the manufacture of the antenna are taken into account. Prog...

  15. Miniaturization of slot and planar monopole antennas : analytical approaches and experimental validation

    OpenAIRE

    Aberbour, Lyazid

    2010-01-01

    Compact antennas for wireless communication devices have gained very high interest. Antenna miniaturization and their performance enhancement remains a challenge, due to the fundamental limitations that bound the realizable performance of an antenna of given size. Radiation efficiency and impedance bandwidth, which are primary considerations in such designs, are critically affected by the antenna size and near-field environment. The main objective of this thesis is to contribute insights and ...

  16. Planetary protection for Europa radar sounder antenna

    Science.gov (United States)

    Aaron, Kim M.; Moussessian, Alina; Newlin, Laura E.; Willis, Paul B.; Chen, Fei; Harcke, Leif J.; Chapin, Elaine; Jun, Insoo; Gim, Yonggyu; McEachen, Michael; Allen, Scotty; Kirchner, Donald; Blankenship, Donald

    2016-05-01

    The potential for habitability puts stringent requirements on planetary protection for a mission to Europa. A long-wavelength radar sounder with a large antenna is one of the proposed instruments for a future Europa mission. The size and construction of radar sounding antennas make the usual methods of meeting planetary protection requirements challenging. This paper discusses a viable planetary protection scheme for an antenna optimized for Europa radar sounding. The preferred methodology for this antenna is exposure to 100 kGy (10 Mrad) in water of gamma radiation using a Cobalt-60 source for both bulk and surface sterilization and exposure to vapor hydrogen peroxide for surface treatment for possible recontamination due to subsequent handling. For the boom-supported antenna design, selected tests were performed to confirm the suitability of these treatment methods. A portion of a coilable boom residual from an earlier mission was irradiated and its deployment repeatability confirmed with no degradation. Elasticity was measured of several fiberglass samples using a four-point bending test to confirm that there was no degradation due to radiation exposure. Vapor hydrogen peroxide treatment was applied to the silver-coated braid used as the antenna radiating element as it was the material most likely to be susceptible to oxidative attack under the treatment conditions. There was no discernable effect. These tests confirm that the radar sounding antenna for a Europa mission should be able tolerate the proposed sterilization methods.

  17. Compact Directional Microwave Antenna for Localized Heating

    Science.gov (United States)

    Fink, Patrick W.; Lin, Gregory Y.; Chu, Andrew W.; Dobbins, Justin A.; Arndt, G. Dickey; Ngo, Phong

    2008-01-01

    A directional, catheter-sized cylindrical antenna has been developed for localized delivery of microwave radiation for heating (and thus killing) diseased tissue without excessively heating nearby healthy tissue. By "localized" is meant that the antenna radiates much more in a selected azimuthal direction than in the opposite radial direction, so that it heats tissue much more on one side than it does on the opposite side. This antenna can be inserted using either a catheter or a syringe. A 2.4-mm prototype was tested, although smaller antennas are possible. Prior compact, cylindrical antennas designed for therapeutic localized hyperthermia do not exhibit such directionality; that is, they radiate in approximately axisymmetric patterns. Prior directional antennas designed for the same purpose have been, variously, (1) too large to fit within catheters or (2) too large, after deployment from catheters, to fit within the confines of most human organs. In contrast, the present antenna offers a high degree of directionality and is compact enough to be useable as a catheter in some applications.

  18. Very Compact and Broadband Active Antenna for VHF Band Applications

    Directory of Open Access Journals (Sweden)

    Y. Taachouche

    2012-01-01

    Full Text Available An active receiving antenna with small size consisting of a monopole loaded with a transistor bipolar is presented in this paper. A transistor is used in order to miniaturize the receiving active antenna size in VHF band. The vertical size of the structure is equal to λ/175, where λ is the wavelength at the lower frequency of the bandwidth. Despite the very small size of the antenna, the frequency bandwidth is very wide and the gain is suitable for FM application with sensitive receivers.

  19. Lithographic antennas for enhancement of solar cell efficiency

    Energy Technology Data Exchange (ETDEWEB)

    Kotter, D.K. [Lockheed Martin Idaho Technologies Co., Idaho Falls, ID (United States); Boreman, G. [Univ. of Central Florida, Orlando, FL (United States). Center for Research and Education in Optics and Lasers

    1998-04-01

    This report documents proof-of-concept demonstration of the use of lithographic antennas for enhancement of solar-cell efficiency. A micro-sized lithographic antenna array was theoretically modeled, designed and fabricated. Experimental research was performed to validate the ability of the antenna array to concentrate infrared and visible energy onto photovoltaic (PV) materials. The research will serve as the basis for the design of a miniature power source for remote sensors.

  20. Review of Low Profile Substrate Integrated Waveguide Cavity Backed Antennas

    OpenAIRE

    Tian Yang Wang; Guo Qing Luo; Xiao Hong Zhang

    2013-01-01

    Low profile cavity backed antennas (CBA) based on substrate integrated waveguide (SIW) technology presented in published papers have been reviewed in this paper. Their operating mechanisms have been discussed and methods for improving the performance, such as bandwidth enhancement, size reduction, and gain improvement, have been presented. These novel antennas retain the advantage of conventional metallic cavity backed antenna, including high gain, high front-to-back ratio, and low cross pola...

  1. Autonomous smart antenna systems for future mobile devices

    OpenAIRE

    Zhou, Wei

    2015-01-01

    Along with the current trend of wireless technology innovation, wideband, compact size, low-profile, lightweight and multiple functional antenna and array designs are becoming more attractive in many applications. Conventional wireless systems utilise omni-directional or sectored antenna systems. The disadvantage of such antenna systems is that the electromagnetic energy, required by a particular user located in a certain direction, is radiated unnecessarily in every direction ...

  2. A coplanar wideband antenna based on metamaterial refractive surface

    Science.gov (United States)

    Salhi, Ridha; Labidi, Mondher; Choubani, Fethi

    2016-01-01

    In this paper, we proceed by presenting a wideband coplanar antenna which can be used in various applications because of its performances such as broad band, small size and low-cost design. Then, we carried out many metamaterial refractive surface (MRS) simulations in order to optimize the antenna performances. Finally, a comparative study between different configurations of the proposed antenna integrated with MRS is presented. The proposed prototype covers the frequency band from 1.6 to 1.8 GHz.

  3. A simple UWB monopole antenna using half-elliptical radiator

    OpenAIRE

    Liu, L.; Sun, YY; Yang, XJ; Cheung, SW

    2013-01-01

    This paper presents the results of a simple ultrawideband (UWB) monopole antenna having an impedance bandwidth from 3.1-40 GHz. The antenna has a half-elliptical shaped radiator with microstrip-fed and a total size of 24×30×0.762 mm3. The extremely wideband characteristic of the antenna is achieved by simply using a tapered transformer and a small square slot on the ground plane. © 2013 IEEE.

  4. Nanotubes of Biomimetic Supramolecules Constructed by Synthetic Metal Chlorophyll Derivatives.

    Science.gov (United States)

    Shoji, Sunao; Ogawa, Tetsuya; Hashishin, Takeshi; Ogasawara, Shin; Watanabe, Hiroaki; Usami, Hisanao; Tamiaki, Hitoshi

    2016-06-01

    Various supramolecular nanotubes have recently been built up by lipids, peptides, and other organic molecules. Major light-harvesting (LH) antenna systems in a filamentous anoxygenic phototroph, Chloroflexus (Cfl.) aurantiacus, are called chlorosomes and contain photofunctional single-wall supramolecular nanotubes with approximately 5 nm in their diameter. Chlorosomal supramolecular nanotubes of Cfl. aurantiacus are constructed by a large amount of bacteriochlorophyll(BChl)-c molecules. Such a pigment self-assembles in a chlorosome without any assistance from the peptides, which is in sharp contrast to the other natural photosynthetic LH antennas. To mimic chlorosomal supramolecular nanotubes, synthetic models were prepared by the modification of naturally occurring chlorophyll(Chl)-a molecule. Metal complexes (magnesium, zinc, and cadmium) of the Chl derivative were synthesized as models of natural chlorosomal BChls. These metal Chl derivatives self-assembled in hydrophobic environments, and their supramolecules were analyzed by spectroscopic and microscopic techniques. Cryo-transmission electron microscopic images showed that the zinc and cadmium Chl derivatives could form single-wall supramolecular nanotubes and their outer and inner diameters were approximately 5 and 3 nm, respectively. Atomic force microscopic images suggested that the magnesium Chl derivative formed similar nanotubes to those of the corresponding zinc and cadmium complexes. Three chlorosomal single-wall supramolecular nanotubes of the metal Chl derivatives were prepared in the solid state and would be useful as photofunctional materials. PMID:27172060

  5. Efficient Chlorophyll Fluorescence Measurements of Sugarcane

    Science.gov (United States)

    As with many crops, chlorophyll fluorescence emission is a promising tool for measuring responses of sugarcane (Saccharum spp.) to biotic and abiotic stresses. Chlorophyll fluorescence can be easily measured using portable fluorometers. However, several factors should be considered in order to op...

  6. Impact of the handset form factor on inverted-F antennas performance

    DEFF Research Database (Denmark)

    Margues, Pablo Fernández; Despointes, E. H.; Barrio, Samantha Caporal Del;

    2012-01-01

    This paper describes the portability of a multiband antenna design over a printed circuit board (PCB) of different sizes. The antenna consists of two inverted-F antennas (IFA) operating at the same resonance frequency, for multiple-input multiple-output (MIMO) operation. The frequency range...... presented in this paper is EGSM900 for the low band and IMT-E for the high band, but the results can be extended to bands 5 and 6 with a tunable antenna. Simulations of the antenna behavior with increasing-size ground plane will be compared to the measurements of three common ground plane sizes: the...

  7. A True Metasurface Antenna

    Science.gov (United States)

    Badawe, Mohamed El; Almoneef, Thamer S.; Ramahi, Omar M.

    2016-01-01

    We present a true metasurface antenna based on electrically-small resonators. The resonators are placed on a flat surface and connected to one feed point using corporate feed. Unlike conventional array antennas where the distance between adjacent antennas is half wavelength to reduce mutual coupling between adjacent antennas, here the distance between the radiating elements is electrically very small to affect good impedance matching of each resonator to its feed. A metasurface antenna measuring 1.2λ × 1.2λ and designed to operate at 3 GHz achieved a gain of 12 dBi. A prototype was fabricated and tested showing good agreement between numerical simulations and experimental results. Through numerical simulation, we show that the metasurface antenna has the ability to provide beam steering by phasing all the resonators appropriately.

  8. Secondary Surveillance Radar Antenna

    OpenAIRE

    Schejbal, Vladimír; Bezoušek, Pavel; Pidanič, Jan; Chyba, Milan

    2013-01-01

    This paper deals with a secondary surveillance radar (SSR) array antenna, which is intended for a system combining the secondary surveillance radar antenna and the primary surveillance radar antenna. It describes the patch array elements and the synthesis for the secondary surveillance radar array, considering both elevation and azimuth patterns for sum, difference, and sidelobe-suppression beams, and suspended stripline couplers. The utilization of multilayer techniques allows the connection...

  9. Antenna Structure Registration (ASR)

    Data.gov (United States)

    Federal Communications Commission — As part of its ongoing efforts to promote air safety, the Federal Communications Commission requires owners to register certain antenna structures (generally those...

  10. Cellular Reflectarray Antenna

    Science.gov (United States)

    Romanofsky, Robert R.

    2010-01-01

    The cellular reflectarray antenna is intended to replace conventional parabolic reflectors that must be physically aligned with a particular satellite in geostationary orbit. These arrays are designed for specified geographical locations, defined by latitude and longitude, each called a "cell." A particular cell occupies nominally 1,500 square miles (3,885 sq. km), but this varies according to latitude and longitude. The cellular reflectarray antenna designed for a particular cell is simply positioned to align with magnetic North, and the antenna surface is level (parallel to the ground). A given cellular reflectarray antenna will not operate in any other cell.

  11. A curl antenna

    OpenAIRE

    Nakano, Hisamatsu; Okuzawa, Shigeru; Ohishi, Katsumi; Mimaki, Hiroaki; Yamauchi, Junji

    1993-01-01

    A radiation element, designated as a curl antenna, is proposed for a circularly polarized antenna. The radiation characteristics of the curl are numerically analyzed. The gain is approximately 8.4 dB, and the 3-dB axial ratio criterion is 6.7%. Two aspects of curl array antennas are also presented: a decoupling factor between two curls and a circular array antenna consisting of 168 curls. Calculations show how the decoupling factor depends on the relative rotation angle of the two curls. The ...

  12. MASTER TELEVISION ANTENNA SYSTEM.

    Science.gov (United States)

    Rhode Island State Dept. of Education, Providence.

    SPECIFICATIONS FOR THE FURNISHING AND INSTALLATION OF TELEVISION MASTER ANTENNA SYSTEMS FOR SECONDARY AND ELEMENTARY SCHOOLS ARE GIVEN. CONTRACTOR REQUIREMENTS, EQUIPMENT, PERFORMANCE STANDARDS, AND FUNCTIONS ARE DESCRIBED. (MS)

  13. Small Device For Short-Range Antenna Measurements Using Optics

    DEFF Research Database (Denmark)

    Yanakiev, Boyan Radkov; Nielsen, Jesper Ødum; Christensen, Morten;

    2011-01-01

    This paper gives a practical solution for implementing an antenna radiation pattern measurement device using optical fibers. It is suitable for anechoic chambers as well as short range channel sounding. The device is optimized for small size and provides a cheap and easy way to make optical antenna...... measurements using off-the-shelf components. Verification measurements are made to confirm the benefits....

  14. Radiation quality factor of spherical antennas with material cores

    DEFF Research Database (Denmark)

    Hansen, Troels Vejle; Kim, Oleksiy S.; Breinbjerg, Olav

    2011-01-01

    This paper gives a description of the radiation quality factor and resonances of spherical antennas with material cores. Conditions for cavity and radiating resonances are given, and a theoretical description of the radiation quality factor, as well as simple expressions describing the relative...... permeability and permittivity for an antenna of fixed electrical size is performed....

  15. Low-profile metamaterial-based L-band antennas

    Science.gov (United States)

    Burokur, Shah Nawaz; Lepage, Anne-Claire; Varault, Stefan; Begaud, Xavier; Piau, Gérard-Pascal; de Lustrac, André

    2016-04-01

    The aim of the present contribution is to show that metasurfaces such as reactive impedance surfaces (RIS) and artificial magnetic conductors can be efficiently used in the design of low-profile circularly polarized L-band antennas. We present the design and simulation of the compact and low-profile antennas. The solution based on RIS will be compared to a circularly polarized microstrip patch antenna using the same materials in order to prove the benefit of metasurfaces. The engineered metasurfaces allow increasing the bandwidths with few modifications on the thickness and the overall antenna size.

  16. Electrically small circularly polarized spherical antenna with air core

    DEFF Research Database (Denmark)

    Kim, O. S.

    2013-01-01

    An electrically small circularly polarized self-resonant spherical antenna with air core is presented. The antenna is a modified multiarm spherical helix exciting TM10 and TE10 spherical modes with equal radiated power, and thus yielding perfect circular polarization over the entire far......-field sphere (except the polar regions, where the radiation is low). The self-resonance is achieved by exciting higher-order TM modes, which provide the necessary electric stored energy in the near-field, while contributing negligibly to the far-field radiation of the antenna. The antenna has electrical size...

  17. Controlling spontaneous emission with plasmonic optical patch antennas

    CERN Document Server

    Belacel, C; Bigourdan, F; Marquier, F; Hugonin, J -P; de Vasconcellos, S Michaelis; Lafosse, X; Coolen, L; Schwob, C; Javaux, C; Dubertret, B; Greffet, J -J; Senellart, P; Maitre, A

    2012-01-01

    We experimentally demonstrate the control of the spontaneous emission rate and the radiation pattern of colloidal quantum dots deterministically positioned in a plasmonic patch antenna. The antenna consists of a thin gold microdisk 30 nm above a thick gold layer. The emitters are shown to radiate through the entire patch antenna in a highly directional and vertical radiation pattern. Strong acceleration of spontaneous emission is observed, depending of the antenna size. Considering the double dipole structure of the emitters, this corresponds to a Purcell factor up to 80 for dipoles perpendicular to the disk.

  18. High-temperature superconducting passive microwave devices, filters and antennas

    International Nuclear Information System (INIS)

    High-temperature superconducting (HTS) passive microwave devices, such as filters and antennas, are promising devices. In particular, HTS filters may be successfully marketed in the near future. Cross-coupled filters, ring filters, and coplanar waveguide filters are good options to reduce filter size. On the other hand, HTS patch antennas which can be cooled by a cryo-cooler are also promising devices as well, since they show higher efficiency than normal antennas. This paper examines the design process and filter properties of HTS filters as well as the gains, directivity, and cooling system of HTS patch antennas. (author)

  19. Miniaturised self-resonant split-ring resonator antenna

    DEFF Research Database (Denmark)

    Kim, Oleksiy S.; Breinbjerg, Olav

    2009-01-01

    A self-resonant miniaturized antenna composed of a broadside-coupled split-ring resonator (SRR) and an excitation arc-shaped monopole is presented. The size of the antenna and its resonance frequency is essentially defined by the SRR dimensions and geometry, while the input resistance at the...... resonance is governed by the arc length of the monopole. Numerical and experimental results are presented for an antenna configuration of 1/23.4 wavelength in diameter (ka~0.134). The antenna is tuned to 50 ohms without any matching network, and its efficiency is measured to be 17.5%....

  20. Review of Low Profile Substrate Integrated Waveguide Cavity Backed Antennas

    Directory of Open Access Journals (Sweden)

    Guo Qing Luo

    2013-01-01

    Full Text Available Low profile cavity backed antennas (CBA based on substrate integrated waveguide (SIW technology presented in published papers have been reviewed in this paper. Their operating mechanisms have been discussed and methods for improving the performance, such as bandwidth enhancement, size reduction, and gain improvement, have been presented. These novel antennas retain the advantage of conventional metallic cavity backed antenna, including high gain, high front-to-back ratio, and low cross polarization level, and also keep the advantages of planar antenna including low profile, light weight, low fabrication cost, and easy integration with planar circuit.

  1. Compact Ultra-Wideband Antenna for Portable Devices

    International Nuclear Information System (INIS)

    This article presents a compact ultra-wideband (UWB) antenna for wireless dongle devices. The printed monopole antenna, with the size of 15 mm × 30 mm, has an impedance bandwidth ranges from 2.9 to 13 GHz. The proposed structure comprises of a hexagonal radiator fed by a microstrip line with a modified ground plane. Such a design can be easily integrated with wireless universal serial bus (USB) devices. Having stable radiation patterns and constant gain within the UWB spectrum are significant characteristics of this antenna. The time domain studies on the designed antenna indicate reduced ringing effect for impulse excitation across the band of interest.

  2. Miniaturised self-resonant split-ring resonator antenna

    OpenAIRE

    Kim, Oleksiy S.; Breinbjerg, Olav

    2009-01-01

    A self-resonant miniaturized antenna composed of a broadside-coupled split-ring resonator (SRR) and an excitation arc-shaped monopole is presented. The size of the antenna and its resonance frequency is essentially defined by the SRR dimensions and geometry, while the input resistance at the resonance is governed by the arc length of the monopole. Numerical and experimental results are presented for an antenna configuration of 1/23.4 wavelength in diameter (ka~0.134). The antenna is tuned to ...

  3. SINGLE LAYER MONOPOLE HEXAGONAL MICROSTRIP PATCH ANTENNA FOR SATELLITE TELEVISION

    Directory of Open Access Journals (Sweden)

    Supriya Jana

    2013-02-01

    Full Text Available A single layer monopole hexagonal patch antenna is thoroughly simulated in this paper. Resonant frequency has been reduced drastically by cutting three unequal slots which are the combinations of one circle and two irregular rectangular slots from the conventional microstrip patch antenna. It is shown that the simulated results are in acceptable agreement. More importantly, it is also shown that the differentially-driven microstrip antenna has higher gain of simulated 3.36 dBi at 9.61GHz and -0.43 dBi at 13.57GHz and beam width of simulated 162.080 at 9.61GHz and 53.450 at 13.57GHz of the single-ended microstrip antenna. Compared to a conventional microstrip patch antenna, simulated antenna size has been reduced by 50.80% with an increased frequency ratio.

  4. Directional borehole antenna - Theory

    International Nuclear Information System (INIS)

    A directional antenna has been developed for the borehole radar constructed during phase 2 of the Stripa project. The new antenna can determine the azimuth of a strong reflector with an accuracy of about 3 degrees as confirmed during experiments in Stripa, although the ratio of borehole diameter to wavelength is small, about 0.03. The antenna synthesizes the effect of a loop antenna rotating in the borehole from four signals measured in turn by a stationary antenna. These signals are also used to calculate an electric dipole signal and a check sum which is used to examine the function of the system. The theory of directional antennas is reviewed and used to design an antenna consisting of four parallel wires. The radiation pattern of this antenna is calculated using transmission line theory with due regard to polarization, which is of fundamental importance for the analysis of directional data. In particular the multipole expansion of the field is calculated to describe the antenna radiation pattern. Various sources of error, e.g. the effect of the borehole, are discussed and the methods of calibrating the antenna are reviewed. The ambiguity inherent in a loop antenna can be removed by taking the phase of the signal into account. Typical reflectors in rock, e.g. fracture zones an tunnels, may be modelled as simple geometrical structures. The corresponding analysis is described and exemplified on measurements from Stripa. Radar data is nowadays usually analyzed directly on the computer screen using the program RADINTER developed within the Stripa project. An algorithm for automatic estimation of the parameters of a reflector have been tested with some success. The relation between measured radar data and external coordinates as determined by rotational indicators is finally expressed in terms of Euler angles. (au)

  5. SAR Study of Mobile Phones as a function of Antenna Q

    DEFF Research Database (Denmark)

    Bahramzy, Pevand; Svendsen, Simon; Jagielski, Ole;

    2015-01-01

    High-Q tunable antennas are good alternatives to low-Q passive antennas because the antenna size can be smaller while covering the required long-term evolution (LTE) frequency bands. However, among other things, specific absorption rate (SAR) can become a challenge due to the relative high current...

  6. A compact planar multi-broad band monopole antenna for mobile devices

    Science.gov (United States)

    Zhong, Xiaoqing; Yao, Bin; Zheng, Qinhong; Yang, Jikong; Cao, Xiangqi

    2015-10-01

    A Multiple-frequency broadband planar monopole antenna is proposed in this Paper. The antenna is stimulated and numerically optimized by HFSS13.0 (High Frequency Structure Simulator). The size of it is 39mm×22mm×1.7mm. The antenna resonates at many frequencies. The parameter S11smart phones

  7. Quality factor of an electrically small magnetic dipole antenna with magneto-dielectric core

    DEFF Research Database (Denmark)

    Kim, Oleksiy S.; Breinbjerg, Olav

    2010-01-01

    In this work, we investigate the radiation Q of electrically small magnetic dipole antennas with magneto-dielectric core versus the antenna electrical size, permittivity and permeability of the core. The investigation is based on the exact theory for a spherical magnetic dipole antenna with...

  8. Substrate integrated antennas and arrays

    CERN Document Server

    Cheng, Yu Jian

    2015-01-01

    Substrate Integrated Antennas and Arrays provides a single source for cutting-edge information on substrate integrated circuits (SICs), substrate integrated waveguide (SIW) feeding networks, SIW slot array antennas, SIC traveling-wave antennas, SIW feeding antennas, SIW monopulse antennas, and SIW multibeam antennas. Inspired by the author's extensive research, this comprehensive book:Describes a revolutionary SIC-based antenna technique with the potential to replace existing antenna technologiesExamines theoretical and experimental results connected to electrical and mechanical performanceExp

  9. Integrated solar panel antennas

    OpenAIRE

    Vaccaro, S.; P. TORRES; Mosig, J. R.; Shah, Arvind; Zürcher,, J.-F.; A. K. Skrivervik; Gardiol, F.; de Maagt, P.; Gerlach, L.

    2008-01-01

    A new antenna which combines solar cells and printed patches is presented. The antenna is designed so as to accommodate the solar cells that provide power to an MMIC amplifier. A 2×4 array is presented, which operates at the frequency of 3.76 GHz and has a bandwidth of 16% and gain up to 30 dBi (active).

  10. Entropy and Fractal Antennas

    OpenAIRE

    Emanuel Guariglia

    2016-01-01

    The entropies of Shannon, Rényi and Kolmogorov are analyzed and compared together with their main properties. The entropy of some particular antennas with a pre-fractal shape, also called fractal antennas, is studied. In particular, their entropy is linked with the fractal geometrical shape and the physical performance.

  11. Annular Planar Monopole Antennas

    OpenAIRE

    Chen, Z. N.; Ammann, Max; Chia, W.Y. W.; See, T.S. P.

    2002-01-01

    A type of annular planar monopole antenna is presented. The impedance and radiation characteristics of the monopole with different holes and feed gaps are experimentally examined. The measured results demonstrate that the proposed antenna is capable of providing significantly broad impedance bandwidth with acceptable radiation performance.

  12. Printed Triband Terminal Antenna

    OpenAIRE

    JOHN, MATTHIAS; Ammann, Max; Farrell, R.

    2005-01-01

    This paper presents a printed triple-band multibranch monopole for use in modern wireless systems. The antenna is designed to operate in three bands which cover virtually all wireless channels. Parameters of the antenna geometry are varied and the effects of these variations on the impedance bandwidth are shown.

  13. A Dual Band Circularly Polarized Microstrip Antenna on an EBG Substrate

    OpenAIRE

    Sudha, T; Vedavathy, TS

    2002-01-01

    A novel circularly polarized (CP), single-fed microstrip antenna on an electromagnetic bandgap (EBG) substrate is presented. The antenna consists of a stacked structure of almost square patches and an EBG substrate for the lower patch. The proposed design has a reduced antenna size as compared to the conventional CP microstrip antenna at a given operating frequency and is of light weight. The impedance and axial ratio bandwidths are large and CP radiation quality is excellent over the entire ...

  14. Deployable Wide-Aperture Array Antennas

    Science.gov (United States)

    Fink, Patrick W.; Dobbins, Justin A.; Lin, Greg Y.; Chu, Andrew; Scully, Robert C.

    2005-01-01

    Inexpensive, lightweight array antennas on flexible substrates are under development to satisfy a need for large-aperture antennas that can be stored compactly during transport and deployed to full size in the field. Conceived for use aboard spacecraft, antennas of this type also have potential terrestrial uses . most likely, as means to extend the ranges of cellular telephones in rural settings. Several simple deployment mechanisms are envisioned. One example is shown in the figure, where the deployment mechanism, a springlike material contained in a sleeve around the perimeter of a flexible membrane, is based on a common automobile window shade. The array can be formed of antenna elements that are printed on small sections of semi-flexible laminates, or preferably, elements that are constructed of conducting fabric. Likewise, a distribution network connecting the elements can be created from conventional technologies such as lightweight, flexible coaxial cable and a surface mount power divider, or preferably, from elements formed from conductive fabrics. Conventional technologies may be stitched onto a supporting flexible membrane or contained within pockets that are stitched onto a flexible membrane. Components created from conductive fabrics may be attached by stitching conductive strips to a nonconductive membrane, embroidering conductive threads into a nonconductive membrane, or weaving predetermined patterns directly into the membrane. The deployable antenna may comprise multiple types of antenna elements. For example, thin profile antenna elements above a ground plane, both attached to the supporting flexible membrane, can be used to create a unidirectional boresight radiation pattern. Or, antenna elements without a ground plane, such as bow-tie dipoles, can be attached to the membrane to create a bidirectional array such as that shown in the figure. For either type of antenna element, the dual configuration, i.e., elements formed of slots in a conductive

  15. Seasonal Composite Chlorophyll Concentrations - Gulf of Maine

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This personal geodatabase contains raster images of chlorophyll concentrations in the Gulf of Maine. These raster images are seasonal composites, and were...

  16. Monolayers and multilayers of chlorophyll [correction of chlorophyl] a on a mercury electrode.

    Science.gov (United States)

    Moncelli, M R; Becucci, L; Dolfi, A; Tadini Buoninsegni, F; Agostiano, A

    2002-05-15

    A novel experimental technique used to investigate chlorophyll films on a hanging mercury drop electrode is described. Two different procedures are employed to prepare self-assembled chlorophyll monolayers and multilayers on the mercury electrode. Upon illuminating the chlorophyll a (Chl)-coated mercury electrode with an appropriate light source, the photocurrents generated by the Chl aggregates are measured under short-circuit conditions in the absence of photoartefacts. The preliminary results obtained by this novel technique are presented. PMID:12009465

  17. Induction of chlorophyll chimeras and chlorophyll mutations in mungbean (Vigna radiata) cv. T44

    International Nuclear Information System (INIS)

    Uniform and healthy seeds of mungbean (Vigna radiata) cv. T44 were exposed to varying doses of gamma rays, ethyl methane sulphonate (EMS) and combination treatment of gamma rays with EMS. The data were recorded for seed germination, plant survival, frequency and spectrum of chlorophyll chimeras in M1 and chlorophyll mutations in M2 generation. Among all, the combination treatments were found most effective for inducing chlorophyll chimeras and chlorophyll mutations than the gamma rays or EMS alone. Of the mutants under reference, the albino, xantha and chlorina showed monogenic recessive while viridis exhibited digenic recessive inheritance. (author). 8 refs., 2 tabs

  18. Low Cost, Low Profile Steerable SATCOM Antenna Project

    Data.gov (United States)

    National Aeronautics and Space Administration — The small size of Unmanned Aerial Vehicle (UAV) platforms along with the need to reduce drag to increase flight time creates a need for low-profile antennas. The...

  19. RF MEMS Based Reconfigurable Antennas

    Science.gov (United States)

    Simons, Rainee N.

    2004-01-01

    The presentation will first of all address the advantages of RF MEMS circuit in antenna applications and also the need for electronically reconfigurable antennas. Next, discuss some of the recent examples of RF MEMS based reconfigurable microstrip antennas. Finally, conclude the talk with a summary of MEMS antenna performance.

  20. Smart antennas in aerospace applications

    OpenAIRE

    Verpoorte, Jaco; Schippers, Harmen; Roeloffzen, Chris G.H.; Marpaung, David A.I.

    2010-01-01

    The interest in Smart Antennas for aerospace applications is growing. This paper describes smart antennas which can be used on aircraft. Two aerospace applications are discussed in more detail: a phased array antenna with optical beam forming and a large vibrating phased array antenna with electronic compensation techniques.

  1. Improved Radiation and Bandwidth of Triangular and Star Patch Antenna

    Directory of Open Access Journals (Sweden)

    M. Ramkumar Prabhu

    2012-06-01

    Full Text Available This study presents a hexagonal shape Defected Ground Structure (DGS implemented on two element triangular patch microstrip antenna array. The radiation performance of the antenna is characterized by varying the geometry and dimension of the DGS and also by locating the DGS at specific position which were simulated. Simulation and measurement results have verified that the antenna with DGS had improved the antenna without DGS. Measurement results of the hexagonal DGS have axial ratio bandwidth enhancement of 10 MHz, return loss improvement of 35%, mutual coupling reduction of 3 dB and gain enhancement of 1 dB. A new wideband and small size star shaped patch antenna fed capacitively by a small diamond shape patch is proposed. To enhance the impedance bandwidth, posts are incorporated under the patch antenna. HFSS high frequency simulator is employed to analyze the proposed antenna and simulated results on the return loss, the E- and H-plane radiation patterns and Gain of the proposed antenna are presented at various frequencies. The antenna is able to achieve in the range of 4-8.8 GHz an impedance bandwidth of 81% for return loss of less than-10 dB.

  2. A Rectangular Planar Spiral Antenna for GIS Partial Discharge Detection

    Directory of Open Access Journals (Sweden)

    Xiaoxing Zhang

    2014-01-01

    Full Text Available A rectangular planar spiral antenna sensor was designed for detecting the partial discharge in gas insulation substations (GIS. It can expediently receive electromagnetic waves leaked from basin-type insulators and can effectively suppress low frequency electromagnetic interference from the surrounding environment. Certain effective techniques such as rectangular spiral structure, bow-tie loading, and back cavity structure optimization during the antenna design process can miniaturize antenna size and optimize voltage standing wave ratio (VSWR characteristics. Model calculation and experimental data measured in the laboratory show that the antenna possesses a good radiating performance and a multiband property when working in the ultrahigh frequency (UHF band. A comparative study between characteristics of the designed antenna and the existing quasi-TEM horn antenna was made. Based on the GIS defect simulation equipment in the laboratory, partial discharge signals were detected by the designed antenna, the available quasi-TEM horn antenna, and the microstrip patch antenna, and the measurement results were compared.

  3. Adaptive antennas and receivers

    CERN Document Server

    Weiner, Melvin M

    2005-01-01

    In our modern age of remote sensing, wireless communication, and the nearly endless list of other antenna-based applications, complex problems require increasingly sophisticated solutions. Conventional antenna systems are no longer suited to high-noise or low-signal applications such as intrusion detection. Detailing highly effective approaches to non-Gaussian weak signal detection, Adaptive Antennas and Receivers provides an authoritative introduction to state-of-the-art research on the modeling, testing, and application of these technologies.Edited by innovative researcher and eminent expert

  4. Atacama Compact Array Antennas

    OpenAIRE

    Saito, Masao; Inatani, Junji; Nakanishi, Kouichiro; Naoi, Takahiro; Yamada, Masumi; Saito, Hiro; Ikenoue, Bungo; Kato, Yoshihiro; Morita, Kou-ichiro; Mizuno, Norikazu; Iguchi, Satoru

    2011-01-01

    We report major performance test results of the Atacama Compact Array (ACA) 7-m and 12-m antennas of ALMA (Atacama Large Millimeter/submillimeter Array). The four major performances of the ACA antennas are all-sky pointing (to be not more than 2.0 arcsec), offset pointing (to be < 0.6 arcsec) surface accuracy (< 25(20) micrometer for 12(7)m-antenna), stability of path-length (15 micrometer over 3 min), and high servo capability (6 degrees/s for Azimuth and 3 degrees/s for Elevation). The high...

  5. Optimisation of Microstrip Antenna

    Directory of Open Access Journals (Sweden)

    H. El Hamchary

    1996-04-01

    Full Text Available When choosing the most appropriate microstrip antenna configuration for particular applications, the kind of excitation of the radiating element is an essential factor that requires careful considerations. For controlling the distribution of energy of the linear or planar array of elements and for coupling energy to the individual elements, a wide variety of feed mechanisms are available. In this paper, the coaxial antenna feeding is assumed and the best (optimised feeding is found. Then, antenna characteristics such as radiation pattern, return loss, input impedance, and VSWR are obtained.

  6. Tunable Liquid Dielectric Antenna

    Directory of Open Access Journals (Sweden)

    Kamal Raj Singh Rajoriya

    2012-06-01

    Full Text Available This paper presents on modified the dielectric properties of liquid with varying salinity that was based on monopole structure. Dielectric resonator antennas (DRAs can be made with a wide range of materials and allow many excitation methods [2]. Pure water does not work at high frequency (> 1 GHz but increase in the salinity of water modifies the dielectric properties of water. Here proposed antenna shows that when the salinity increases in form of molar solution, the antenna was tuned at different frequency with increases return loss.

  7. Antennas from theory to practice

    CERN Document Server

    Huang, Yi

    2008-01-01

    Practical, concise and complete reference for the basics of modern antenna design Antennas: from Theory to Practice discusses the basics of modern antenna design and theory. Developed specifically for engineers and designers who work with radio communications, radar and RF engineering, this book offers practical and hands-on treatment of antenna theory and techniques, and provides its readers the skills to analyse, design and measure various antennas. Key features: Provides thorough coverage on the basics of transmission lines, radio waves and propag

  8. Fluorescence spectral properties of outer antenna LHC II

    CERN Document Server

    He Jun Fang; Zhang, Shu; He Fang Tao; Ren Zhao You; Li Liang Bi; Kuang Ting Yun

    2002-01-01

    Outer antenna LHC II acts to absorb and transfer energy for photosynthesis. The authors studied the fluorescence properties of LHC II of spinach with scanning imaging fluorescence spectroscopy. After it had been excited by 514.5 nm laser, the integral fluorescence spectrum of LHC II was detected. It was shown that energy transfer existed between carotenoid and chlorophyll. Seven bands of LHC II fluorescence emission were resolved by Gauss combination, viz. 656.7, 664.6, 671.5, 677.2, 683.5, 689.6, 695.3 nm, and the percentages of them were 3.0%, 13.1%,13.3%, 21.1%, 13.2%, 33.3%, 3.0% respectively. The emission of 658.7 nm was attributed to chlorophyll b, the other emission bands were produced by chlorophyll a molecules with the maximum absorption 662, 670/671, 676, 680 nm and over 690 nm. The band 656.7 nm, whose percentage was 3.0%, shows that the most energy was absorbed by chlorophyll a. The percentage of band 689.6 nm was the most, which was possibly correlated with one type of self protective mechanism o...

  9. Nonlinear plasmonic antennas

    Directory of Open Access Journals (Sweden)

    Shakeeb Bin Hasan

    2014-12-01

    Full Text Available Contrary to traditional optical elements, plasmonic antennas made from nanostructured metals permit the localization of electromagnetic fields on length scales much smaller than the wavelength of light. This results in huge amplitudes for the electromagnetic field close to the antenna being conducive for the observation of nonlinear effects already at moderate pump powers. Thus, these antennas exhibit a promising potential to achieve optical frequency conversion and all-optical control of light at the nano-scale. This opens unprecedented opportunities for ultrafast nonlinear spectroscopy, sensing devices, on-chip optical frequency conversion, nonlinear optical metamaterials, and novel photon sources. Here, we review some of the recent advances in exploiting the potential of plasmonic antennas to realize robust nonlinear applications.

  10. Fractal multiband patch antenna

    OpenAIRE

    Borja, C.; Puente Baliarda, Carles; Romeu Robert, Jordi; Anguera Pros, Jaume

    2000-01-01

    The multiband behaviour of the Sierpinski patch antenna is described in this paper. Experimental results show that the self similarity properties of the fractal shape are translated into its electromagnetic behaviour. Peer Reviewed

  11. Atacama Compact Array Antennas

    CERN Document Server

    Saito, Masao; Nakanishi, Kouichiro; Naoi, Takahiro; Yamada, Masumi; Saito, Hiro; Ikenoue, Bungo; Kato, Yoshihiro; Morita, Kou-ichiro; Mizuno, Norikazu; Iguchi, Satoru

    2011-01-01

    We report major performance test results of the Atacama Compact Array (ACA) 7-m and 12-m antennas of ALMA (Atacama Large Millimeter/submillimeter Array). The four major performances of the ACA antennas are all-sky pointing (to be not more than 2.0 arcsec), offset pointing (to be < 0.6 arcsec) surface accuracy (< 25(20) micrometer for 12(7)m-antenna), stability of path-length (15 micrometer over 3 min), and high servo capability (6 degrees/s for Azimuth and 3 degrees/s for Elevation). The high performance of the ACA antenna has been extensively evaluated at the Site Erection Facility area at an altitude of about 2900 meters. Test results of pointing performance, surface performance, and fast motion capability are demonstrated.

  12. Microwave antenna holography

    Science.gov (United States)

    Rochblatt, David J.; Seidel, Boris L.

    1992-01-01

    This microwave holography technique utilizes the Fourier transform relation between the complex far field radiation pattern of an antenna and the complex aperture field distribution. Resulting aperture phase and amplitude distribution data can be used to precisely characterize various crucial performance parameters, including panel alignment, panel shaping, subreflector position, antenna aperture illumination, directivity at various frequencies, and gravity deformation effects. The methodology of data processing presented here was successfully applied to the Deep Space Network (DSN) 34-m beam waveguide antennas. The antenna performance was improved at all operating frequencies by reducing the main reflector mechanical surface rms error to 0.43 mm. At Ka-band (32 GHz), the estimated improvement is 4.1 dB, resulting in an aperture efficiency of 52 percent. The performance improvement was verified by efficiency measurements and additional holographic measurements.

  13. Intelsat VI antenna system

    Science.gov (United States)

    Caulfield, M. F.; Lane, S. O.; Taormina, F. A.

    The antenna system design of a series of five new communications satellites known as Intelsat VI is described in detail. Each satellite will utilize 50 transponders operating in the C and K band portions of the frequency spectrum. The transponders are interconnectible using either static switch matrices or a network which provides satellite switched time division multiple access capability. The antenna coverages, characteristics, and special design features are shown and discussed.

  14. QTL Mapping of Chlorophyll Contents in Rice

    Institute of Scientific and Technical Information of China (English)

    SHEN Bo; ZHUANG Jie-yun; ZHANG Ke-qin; DAI Wei-min; LU Ye; FU Li-qing; DING Jia-ming; ZHENG Kang-le

    2007-01-01

    The objectives of this study were to investigate the genetic factors controlling the chlorophyll content of rice leaf using QTL analysis. A linkage map consisting of 207 DNA markers was constructed by using 247 recombinant inbred lines (RILs) derived from an indica-indica rice cross of Zhenshan97B×Milyang 46. In 2002 and 2003, the contents of chlorophyll a and b of the parents and the 247 RILs were measured on the top first leaf, top second leaf, and top third leaf, respectively. The software QTLMapper 1.6 was used to detect quantitative trait loci (QTLs), additive by environment (AE) interactions, and epistatic by environment (AAE) interactions. A total of eight QTLs in four intervals were detected to have significant additive effects on chlorophyll a and b contents at different leaf positions, with 1.96-9.77% of phenotypic variation explained by a single QTL, and two QTLs with significant AE interactions were detected. Epistasis analysis detected nine significant additive-by-additive interactions on chlorophyll a and b contents, and one pair of QTLs with significant AAE interactions was detected. On comparison with QTLs for yield traits detected in the same population, it was found in many cases that the QTLs for chlorophyll a and b contents and those for yield traits were located in the same chromosome intervals.

  15. Bowel perforation detection using metabolic fluorescent chlorophylls

    Science.gov (United States)

    Han, Jung Hyun; Jo, Young Goun; Kim, Jung Chul; Choi, Sujeong; Kang, Hoonsoo; Kim, Yong-Chul; Hwang, In-Wook

    2016-03-01

    Thus far, there have been tries of detection of disease using fluorescent materials. We introduce the chlorophyll derivatives from food plants, which have longer-wavelength emissions (at >650 nm) than those of fluorescence of tissues and organs, for detection of bowel perforation. To figure out the possibility of fluorescence spectroscopy as a monitoring sensor of bowel perforation, fluorescence from organs of rodent models, intestinal and peritoneal fluids of rodent models and human were analyzed. In IVIS fluorescence image of rodent abdominal organ, visualization of perforated area only was possible when threshold of image is extremely finely controlled. Generally, both perforated area of bowel and normal bowel which filled with large amount of chlorophyll derivatives were visualized with fluorescence. The fluorescence from chlorophyll derivatives penetrated through the normal bowel wall makes difficult to distinguish perforation area from normal bowel with direct visualization of fluorescence. However, intestinal fluids containing chlorophyll derivatives from food contents can leak from perforation sites in situation of bowel perforation. It may show brighter and longer-wavelength regime emissions of chlorophyll derivatives than those of pure peritoneal fluid or bioorgans. Peritoneal fluid mixed with intestinal fluids show much brighter emissions in longer wavelength (at>650 nm) than those of pure peritoneal fluid. In addition, irrigation fluid, which is used for the cleansing of organ and peritoneal cavity, made of mixed intestinal and peritoneal fluid diluted with physiologic saline also can be monitored bowel perforation during surgery.

  16. Inkjet-Printed Wideband Antenna on Resin-Coated Paper Substrate for Curved Wireless Devices

    KAUST Repository

    Abutarboush, Hattan

    2015-04-28

    A low-cost, inkjet-printed multiband monopole antenna for conformal wireless applications is presented for the first time. The antenna is implemented on a low cost resin coated paper substrate which can be used for conformal devices. The antenna developed here is composed of four branch lines on the radiator and three L-shaped slots on the ground plane that help to generate multiple bands without increasing the size of the antenna. The antenna has a compact size, making it suitable for handheld and wearable wireless devices. Details of the inkjet printing fabrication processes and related issues are presented. The antennas were characterized under flat and bent conditions and the results indicate that the antennas can cover most bands for mobile and wireless applications such as PCS, UMTS, GSM1900 and WLAN

  17. Antenna-in-package system integrated with meander line antenna based on LTCC technology

    Institute of Scientific and Technical Information of China (English)

    Gang DONG; Wei XIONG; Zhao-yao WU; Yin-tang YANG

    2016-01-01

    We present an antenna-in-package system integrated with a meander line antenna based on low temperature co-fired ceramic (LTCC) technology. The proposed system employs a meander line patch antenna, a packaging layer, and a laminated multi-chip module (MCM) for integration of integrated circuit (IC) bare chips. A microstrip feed line is used to reduce the interaction between patch and package. To decrease electromagnetic coupling, a via hole structure is designed and analyzed. The meander line antenna achieved a bandwidth of 220 MHz with the center frequency at 2.4 GHz, a maximum gain of 2.2 dB, and a radiation efficiency about 90% over its operational frequency. The whole system, with a small size of 20.2 minx6.1 mmx2.6 mm, can be easily realized by a standard LTCC process. This antenna-in-package system integrated with a meander line antenna was fabricated and the experimental results agreed with simulations well.

  18. Antenna-in-package system integrated with meander line antenna based on LTCC technology

    Institute of Scientific and Technical Information of China (English)

    Gang DONG; Wei XIONG; Zhao-yao WU; Yin-tang YANG

    2016-01-01

    We present an antenna-in-package system integrated with a meander line antenna based on low temperature co-fi red ceramic (LTCC) technology. The proposed system employs a meander line patch antenna, a packaging layer, and a laminated multi-chip module (MCM) for integration of integrated circuit (IC) bare chips. A microstrip feed line is used to reduce the interaction between patch and package. To decrease electromagnetic coupling, a via hole structure is designed and analyzed. The meander line antenna achieved a bandwidth of 220 MHz with the center frequency at 2.4 GHz, a maximum gain of 2.2 dB, and a radiation efficiency about 90% over its operational frequency. The whole system, with a small size of 20.2 mm×6.1 mm×2.6 mm, can be easily realized by a standard LTCC process. This antenna-in-package system integrated with a meander line antenna was fabricated and the experimental results agreed with simulations well.

  19. Compact Ultra-wideband Microstrip Antenna with Metamaterials

    International Nuclear Information System (INIS)

    An improved compact ultra-wideband (UWB) microstrip antenna with metamaterials is proposed. The total size is slightly reduced and the measured impedance bandwidth operates from 3.84 to 22.77 GHz for a return loss of less than −10 dB. Compared with the original patch antenna, the bandwidth of this antenna is about six times broader. Moreover, the antenna has an average gain of 6.2 dB, which is 1.2 dB larger than the original one. Both strong radiation in the horizontal direction and practical characteristics are observed. Thus, this antenna would have some specific applications for UWB wireless communications in the future

  20. Measurement of the ultrafast temporal response of a plasmonic antenna

    International Nuclear Information System (INIS)

    A measurement on the temporal response of a plasmonic antenna at the femtosecond time scale is reported. The antenna consists of a square array of nanometer-size gold rods. The far-field dispersion of light reflected from the plasmonic antenna is found to be less than that of a 1.2 mm thick glass slide. Assuming a simple oscillating dipole model this implies that the near-field of the antenna may be used as an electron switch that responds faster than 20 fs. Alternatively, ultrafast electron diffraction may be used to investigate the near-field dynamics of the plasmonic antenna. (copyright 2012 by WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  1. Miniaturized Circularly Polarized Microstrip RFID Antenna Using Fractal Metamaterial

    Directory of Open Access Journals (Sweden)

    Guo Liu

    2013-01-01

    Full Text Available A novel miniaturized circularly polarized (CP microstrip antenna that can handle UHF band (920–925 MHz, corresponding to the assigned band for RFID in China has been designed, fabricated, and measured in this paper. The miniaturization of antenna is achieved by a special cross-shaped fractal metamaterial structure that is inserted between the patch and ground plane. The measured results show that the antenna possesses an impedance bandwidth of 8.7% with VSWR 1.5 : 1 and 3-dB axial bandwidth of 3.8%. Furthermore, the proposed antenna has 10.2% size reduction compared with traditional patch antenna. The tested results are in good agreement with that of the simulations.

  2. Uniplanar circularly polarized slot-ring antenna architectures

    Science.gov (United States)

    Fries, Matthias K.; Vahldieck, Rüdiger

    2002-04-01

    This paper presents a novel printed uniplanar antenna architecture for circular polarization. The structure consists of a single-fed slot-ring antenna with asymmetrically placed perturbations. The influence of different kinds of perturbations and substrates on the size of the antenna, its impedance bandwidth, and its axial ratio bandwidth is investigated. Various feed circuits based on coplanar waveguides (CPWs), coaxial line, and microstrip are investigated as well. Low-cost applications such as tagging antennas at 2.45 GHz are tested in combination with a coaxial line and CPW feed circuit. It was found that antennas achieving an impedance bandwidth over 60% and an axial ratio bandwidth up to 15% can be realized without the need of airbridges and rf-substrates.

  3. A Small UWB Antenna with Dual Band-Notched Characteristics

    Directory of Open Access Journals (Sweden)

    J. Xu

    2012-01-01

    Full Text Available A small novel ultrawideband (UWB antenna with dual band-notched functions is proposed. The dual band rejection is achieved by etching two C-shaped slots on the radiation patch with limited area. A single band-notched antenna is firstly presented, and then an optimized dual band-notched antenna is presented and analyzed. The measured VSWR shows that the proposed antenna could operate from 3.05 to 10.7 GHz with VSWR less than 2, except two stopbands at 3.38 to 3.82 GHz and 5.3 to 5.8 GHz for filtering the WiMAX and WLAN signals. Radiation patterns are simulated by HFSS and verified by CST, and quasiomnidirectional radiation patterns in the H-plane could be observed. Moreover, the proposed antenna has a very compact size and could be easily integrated into portable UWB devices.

  4. Characteristics Study of Portable Hand-Held Phone Antenna by MoM

    Institute of Scientific and Technical Information of China (English)

    李玉莹; 徐晓文

    2003-01-01

    The characteristics of one kind of handset antenna are analyzed by the method of moments. By using the Pocklington equation and the Galerkin method, the current distribution on the handset antenna is calculated, the input impedance and radiation patterns are obtained. In addition, the characteristics of monopoles mounted on conducting chassis box with different sizes are analyzed. The results show that the size of the conducting chassis box has significant effect on the performance of the handset antenna. Therefore, appropriately changing the size of the conducting chassis box may improve the performance of the handset antenna.

  5. Hybrid Deployable Foam Antennas and Reflectors

    Science.gov (United States)

    Rivellini, Tommaso; Willis, Paul; Hodges, Richard; Spitz, Suzanne

    2006-01-01

    Hybrid deployable radio antennas and reflectors of a proposed type would feature rigid narrower apertures plus wider adjoining apertures comprising reflective surfaces supported by open-cell polymeric foam structures (see figure). The open-cell foam structure of such an antenna would be compressed for compact stowage during transport. To initiate deployment of the antenna, the foam structure would simply be released from its stowage mechanical restraint. The elasticity of the foam would drive the expansion of the foam structure to its full size and shape. There are several alternatives for fabricating a reflective surface supported by a polymeric foam structure. One approach would be to coat the foam with a metal. Another approach would be to attach a metal film or a metal-coated polymeric membrane to the foam. Yet another approach would be to attach a metal mesh to the foam. The hybrid antenna design and deployment concept as proposed offers significant advantages over other concepts for deployable antennas: 1) In the unlikely event of failure to deploy, the rigid narrow portion of the antenna would still function, providing a minimum level of assured performance. In contrast, most other concepts for deploying a large antenna from compact stowage are of an "all or nothing" nature: the antenna is not useful at all until and unless it is fully deployed. 2) Stowage and deployment would not depend on complex mechanisms or actuators, nor would it involve the use of inflatable structures. Therefore, relative to antennas deployed by use of mechanisms, actuators, or inflation systems, this antenna could be lighter, cheaper, amenable to stowage in a smaller volume, and more reliable. An open-cell polymeric (e.g., polyurethane) foam offers several advantages for use as a compressible/expandable structural material to support a large antenna or reflector aperture. A few of these advantages are the following: 3) The open cellular structure is amenable to compression to a very

  6. The spontaneous chlorophyll mutation frequency in barley

    DEFF Research Database (Denmark)

    Jørgensen, Jørgen Helms; Jensen, Hans Peter

    1986-01-01

    A total of 1866 barley plants were progeny tested in the greenhouse. Twenty-five plants segregated for newly arisen, spontaneous chlorophyll mutant genes. Among the total of 470,129 seedlings screened there were 79 mutants (1.7 .+-. 0.6 .times. 10-4). The data are added to data from three similar...... materials and the resulting estimate of the chlorophyll mutant frequency is 1.6 .times. 10-4 in about 1.43 million seedlings. The estimate of the chlorophyll mutation rate per generation is close to 67.3 .times. 10-4 per diploid genome or in the order of 6 .times. 10-7 per locus and haploid genome....

  7. JET ICRH antenna for pumped-divertor geometry

    International Nuclear Information System (INIS)

    The plasma configuration in the proposed JET programme extending up to 1996 will be a Single-Null (bottom) X-point with a pump divertor. This geometry has important limitations for coupling the RF power by the present ICRH antennas as the plasma size would be smaller and it will be significantly vertically asymmetric. It is clear that the present ICRH antenna (A1) system should be made compatible with the new proposed plasma configuration to utilise the full potential of the 32 MW (generator), 20 s pulse-length, 25-55 MHz JET ICRH installed facility for plasma heating and possible current drive applications in the proposed new phase of the JET programme. The present state-of-the-art knowledge of the antenna design at JET will be used for A2-antenna design which would also incorporate the ICRH current drive features as a prelude to the design of an ICRH launcher of the Next-Step devices. In this design, antennas would be made wider and deeper which would improve the coupling and it is estimated that more than 20 MW can be coupled to X-point plasmas from the ICRH plant. The current drive capability would be improved (≅ 1 MA) by the use of septums which allow arbitrary phasing between each central conductors. The design philosophy that is being followed in the design of JET A2-antennas is outlined and the present status and the main features of the physics and engineering design of A2-antenna are discussed. The antenna-plasma coupling and the antenna-directivity for the new antenna are then presented. Finally, a time-schedule for the design, construction and installation of the antennas is also given. (author)

  8. CPW-fed Wideband Antenna with U-shaped Ground Plane

    OpenAIRE

    Shagun Maheshwari; Priyanka Jain; Archana Agarwal

    2014-01-01

    This paper proposes the design of CPW-fed wideband antenna with U-shaped ground plane. The proposed antenna is a simple printed antenna, which is fed by a 50Ω CPW line. The Antenna has a compact size of 13mm×25mm. To obtain wide bandwidth, a slot is cut in ground plane and radiating patch is modified. The proposed antenna yields the operating frequency range from 7.3GHz to 15.1GHz, which offers the bandwidth of 7.79GHz. Simulation has been performed by using CST Microwave Studio Software. Thi...

  9. Microstrip Folded Dipole Antenna for 35 GHz MMW Communication

    Directory of Open Access Journals (Sweden)

    Guang Hua

    2013-01-01

    Full Text Available A microstrip asymmetric folded dipole antenna on chip is proposed in this paper. The construction of balun feed line is adopted to provide wideband. A new design procedure based on the odd-even mode method to calculate the input impedance of an asymmetric strip folded dipole antenna is presented. The folded dipole antenna has the advantage of small size, low profile, low cost, and so forth. The measured results show that a miniaturized antenna has the bandwidth of more than 14.2% (VSWR ≤ 2; gain of the antenna is 5.7 dB at 35 GHz.

  10. SANTANA- Smart Antenna Terminal Design

    OpenAIRE

    Liu, Ying

    2006-01-01

    This project is embedded in SANTANA (Smart Antenna Terminal) project. The project goal is to design a Ka-band circularly polarized antenna radiator for the receiver SANTANA system. The research work focuses on two types of circularly polarized antennas: aperture-coupled patch antenna and CPW-fed patch antenna. A two steps design process is used. Firstly, only the antennas and their feed structure are designed and optimized. Secondly, a via-transition to connect to a MMIC layer is added. When ...

  11. Modeling of compact loop antennas

    Science.gov (United States)

    Baity, F. W.

    1987-09-01

    A general compact loop antenna model which treats all elements of the antenna as lossy transmission lines has been developed. In addition to capacitively tuned resonant double loop (RDL) antennas, the model treats sub-tuned RDL antennas. Calculations using the model have been compared with measurements on full-scale mock-ups of RDL antennas for ATF and TFTR in order to refine the transmission line parameters. Results from the model are presented for RDL antenna designs for ATF, TFTR, Tore Supra, and the Compact Ignition Tokamak (CIT).

  12. Modeling of compact loop antennas

    International Nuclear Information System (INIS)

    A general compact loop antenna model which treats all elements of the antenna as lossy transmission lines has been developed. In addition to capacitively-tuned resonant double loop (RDL) antennas the model treats stub-tuned resonant double loop antennas. Calculations using the model have been compared with measurements on full-scale mockups of resonant double loop antennas for ATF and TFTR in order to refine the transmission line parameters. Results from the model are presented for RDL antenna designs for ATF, TFTR, Tore Supra, and for the Compact Ignition Tokamak

  13. Modeling of compact loop antennas

    International Nuclear Information System (INIS)

    A general compact loop antenna model which treats all elements of the antenna as lossy transmission lines has been developed. In addition to capacitively tuned resonant double loop (RDL) antennas, the model treats sub-tuned RDL antennas. Calculations using the model have been compared with measurements on full-scale mock-ups of RDL antennas for ATF and TFTR in order to refine the transmission line parameters. Results from the model are presented for RDL antenna designs for ATF, TFTR, Tore Supra, and the Compact Ignition Tokamak

  14. The Segmented Bifilar Contrawound Toroidal Helical Antenna.

    Science.gov (United States)

    Vanvoorhies, Kurt Louis

    The segmented bifilar contrawound toroidal helical antenna, a.k.a. QuadContra antenna creates a toroidal magnetic current whose radiated electromagnetic fields emulate those of an electric dipole located normal to the plane of the toroidal helix. This antenna is a magnetic dual of the constant current electric loop antenna. Its principal advantages of reduced size and low profile result from both its circular geometry and from the velocity factor of its slow wave contrawound helical structure. This antenna is constructed by winding two conductors in contrawound relation to each other on a toroidal form, dividing the winding into an even number of segments, and reversing the pitch sense of each conductor from one segment to another. Feed ports are located on the conductors at the segment boundaries, and are connected in alternate phase to a central signal terminal via balanced and tuned transmission line elements. At resonance, each winding segment supports a quarter-wave sinusoidal current distribution. Toroidal electric current components are canceled, and poloidal current components are enhanced in the resulting anti-symmetric mode current distribution. This study measured and simulated the velocity factor, input impedance, bandwidth and simulated the radiation gain and pattern for a variety of linear and toroidal structures. The velocity factor, modeled as a power function of the ratio of axial winding length to wire length, was two to three times slower for the anti-symmetric mode contrawound helix than for a comparable monofilar helix. The radiation characteristics of the antenna were simulated using the OSU ESP4 Moment Method based program, after making extensive improvements to accommodate a wide variety of antenna configurations and to automatically find resonant frequencies. The simulated QuadContra antenna radiates with vertically polarization in a dipole-like pattern having a gain about 2 dB less than the dipole. The gain falls off dramatically for

  15. Plankton studies in San Francisco Bay; I, Chlorophyll distributions and hydrographic properties, July 1977-December 1979

    Science.gov (United States)

    Alpine, Andrea E.; Cloern, James E.; Cole, Brian E.

    1981-01-01

    This report summarizes the distribution of phytoplankton biomass and selected hydrographic properties measured in the San Francisco Bay Estuary, on a near-monthly basis, from July 1977 through December 1979. Parameters measured were: chlorophyll a, phaeopigments, in-vivo fluorescence, turbidity, size distribution of phytoplankton, salinity and temperature. (USGS)

  16. Circularly Polarized Broadband RFID Microstrip Tag Antenna

    Directory of Open Access Journals (Sweden)

    B. Rajini

    2014-04-01

    Full Text Available In recent years, the application of radio frequency identification (RFID operating in the ultra-high frequency (UHF band (860-960MHz are expanding exponentially, due to the advantages such as long reading distance, high data transfer rate, and small tag size. So the design of a CP tag antenna with broadband characteristic is presently one of the most challenging topics. This project presents a square patch passive RFID tag antenna designed for UHF band. To achieve compact size broadband and circular polarization (CP radiation, the square patch is embedded with a cross slot, while an L-shaped open-end microstrip line coupled to the patch. By selecting an appropriate length for the microstrip line and its coupling distance with the radiating element, easy control on the input impedance of the designed tag antenna which leads to excellent impedance matching is achieved. The measured 10-dB return-loss bandwidth of the tag antenna is 27MHz (from 901–928 MHz.

  17. Dual-Frequency Operation of Bow-Tie Microstrip Antenna%蝶形微带天线的双频工作

    Institute of Scientific and Technical Information of China (English)

    钟顺时; 张需溥

    2005-01-01

    Characteristics of a single-feed dual-frequency bow-tie microstrip antenna are studied. By using the variation method, simple formulas for resonant frequencies of the bow-tie microstrip antenna are derived. It is shown that the dual-frequency ratio can be controlled easily by choosing the parameters of the antenna. This design gives compact antenna size and simple antenna structure. Experimental results are presented, verifying the validity of the design.

  18. Imaging antenna arrays

    Science.gov (United States)

    Rutledge, D. B.; Muha, M. S.

    1982-01-01

    Many millimeter and far-infrared imaging systems are limited in sensitivity and speed because they depend on a single scanned element. Because of recent advances in planar detectors such as Schottky diodes, superconducting tunnel junctions, and microbolometers, an attractive approach to this problem is a planar antenna array with integrated detectors. A planar line antenna array and optical system for imaging has been developed. The significant advances are a 'reverse-microscope' optical configuration and a modified bow-tie antenna design. In the 'reverse-microscope' configuration, a lens is attached to the bottom of the substrate containing the antennas. Imaging is done through the substrate. This configuration eliminates the troublesome effects of substrate surface waves. The substrate lens has only a single refracting surface, making possible a virtually aplanatic system, with little spherical aberration or coma. The array is characterized by an optical transfer function that is easily measured. An array with 19 dB crosstalk levels between adjacent antennas has been tested and it was found that the array captured 50 percent of the available power. This imaging system was diffraction limited.

  19. Long-term dynamics of chlorophyll concentration in the ocean surface layer (by space data)

    Science.gov (United States)

    Shevyrnogov, A.; Vysotskaya, G.

    To preserve the biosphere and to use it efficiently, it is necessary to gain a deep insight into the dynamics of the primary production process on our planet. Variability of chlorophyll concentration in the ocean is one of the most important components of this process. These investigations are, however, very labor-consuming, because of the difficulties related to the accessibility of the water surface and its large size. In this work long-term changes in chlorophyll concentration in the surface layer of the ocean have been analyzed on the basis of the CZCS data for 7.5 years from 1979 to 1986 and the SeaWiFS data from 1997 to 2004. It has been shown that the average chlorophyll concentration calculated in all investigated areas varies moderately. However, when analyzing spatially local trends, the areas have been detected that have significant rise and fall of chlorophyll concentrations. Some interesting features of the long-term dynamics of chlorophyll concentration have been found. The opposite directions of long-term trends (essential increase or decrease) cannot be explained only by large-scale hydrological phenomena in the ocean (currents, upwellings, etc.). The measured chlorophyll concentration results from the balance between production and destruction processes. Which process dominates is determined by various hydrophysical, hydrobiological, and climatic processes, leading to sharp rises or falls of the concentration. It is important to estimate the scale of the areas in which this or that process dominates. Therefore, the study addresses not only the dynamics of the mean value but also the dynamics of the areas in which the dominance of certain factors has led to a sharp fall or rise in chlorophyll concentration. Thus, the obtained results can be used to estimate long-term changes in the ocean biota.

  20. Design of Two Novel Dual Band-Notched UWB Antennas

    Directory of Open Access Journals (Sweden)

    Bing Li

    2012-01-01

    Full Text Available Two novel dual band-notched ultra-wideband (UWB printed monopole antennas with simple structure and small size are presented. The size of both antennas is 25×25×0.8 mm3. The bandwidth of one of the proposed antenna can be from 2.7 GHz to 36.8 GHz, except the bandwidth of 3.2–3.9 GHz for WiMAX applications and 5.14–5.94 GHz for WLAN applications. The bandwidth of the other is ranging for 2.7 to 41.1 GHz, except the bandwidth of 3.2–3.9 GHz for WiMAX applications and 4.8–5.9 GHz for WLAN applications. Bandwidths of the antennas are about 512% and 455% wider than those of conventional band-notched UWB antennas, respectively. In addition, the time-domain characteristics of the two antennas are investigated to show the difference between both antennas.

  1. A Compact Annular Ring Microstrip Antenna for WSN Applications

    Directory of Open Access Journals (Sweden)

    Daihua Wang

    2012-06-01

    Full Text Available A compact annular ring microstrip antenna was proposed for a wireless sensor network (WSN application in the 2.4 GHz band. In this paper the major considerations of the conformal antenna design were the compact size and the impact on antenna’s performance of a steel installation base. By using a chip resistor of large resistance (120 Ω the antenna size was reduced to 38% of that a conventional annular ring patch antenna. With the addition of the steel installation base the resonant frequency of the antenna increases about 4.2% and the bandwidth reduces from 17.5% to 11.7% by adjusting the load resistance simultaneously. Several key parameters were discussed and optimized, and the antenna was fabricated and its performance measured. The antenna is well matched at 2.4 GHz with 34.2 dB return loss and –2.5 dBi peak gain. Meanwhile, it exhibits excellent radiation patterns with very low cross-polarization levels.

  2. Technologies and Applications of Microwave Photonic Antennas

    OpenAIRE

    Y. Yashchyshyn; Chizh, A.; Malyshev, S.; Modelski, J

    2010-01-01

    This paper describes the development of microwave photonic antennas concepts and their applications. The experimental study of the transmitting and receiving photonic antenna are shown. The transmitting photonic antenna consists of photodiode integrated with microstrip E-shaped patch antenna, and receiving photonic antenna consists of laser diode integrated directly with the Vivaldi antenna.

  3. Dual polarization flat plate antenna

    Science.gov (United States)

    Kelly, Kenneth C.

    Rectangular waveguides with radiating slots are used in groups to form planar array microwave antennas with large apertures and small depth. Such flat plate antennas are widely used on spacecraft and aircraft. Typically, flat plate antennas provide fixed linear polarization. The present paper describes a new flat plate antenna which produces two coincident beams that are distinguished by their orthogonal linear polarizations. The antenna has two ports, one for each of the coicident beams. Completely external to the antenna, connecting a simple network to those terminal ports enables the antenna to provide right circular polarization from one port and left from the other. A different external network enables the antenna to have arbitrarily adjustable polarizations.

  4. Vector potential analysis of the helicon antenna in vacuum

    CERN Document Server

    Johnson, Robert W

    2011-01-01

    The helicon antenna is a well-known device in the field of electric propulsion. Here we investigate the vector potential produced in vacuum by such an antenna with typical size parameters. Both a static and a dynamic analysis are performed. The dynamic calculation is evaluated at both the usual operating frequency and one which is slightly greater. At the higher frequency, a pulse of electromagnetic energy is found to propagate along the cylindrical axis in either direction. The possible adaptation of the helicon antenna as a RF injection device for burning plasma is discussed.

  5. A compact circularly polarized patch antenna with ring reflector

    OpenAIRE

    Jia, F.; Han, W.; Li, Y.; Sun, S.

    2014-01-01

    A miniaturized antenna with circular polarization and directional pattern is presented in this paper. The conventional ground plane is replaced by a rectangular ring reflector to form the directional pattern. Since the side length of the ring reflector is around quarter-waveleng, the total size of the proposed antenna is reduced dramatically, which is about λg/2 × λg/2 in the horizontal plane. In addition, the performance of the proposed antenna is still comparable with the convetional micros...

  6. A Wideband Single Fed L Slot Circularly Polarized Antenna

    OpenAIRE

    Nisha; Meenakshi saini

    2014-01-01

    A single-fed circularly polarized (CP) patch antenna is designed and built using L-slot loaded patch technique. The antenna is designed on a high dielectric constant (εr = 10.02) substrate which achieves a reasonable bandwidth and axial ratio bandwidth with respect to a U slot antenna. At the operating frequency of 1.575 GHz with the size of the patch is 25mm X 25mm, while ground plane of 60mm X 60mm and the thickness of the substrate is 9.12mm. Bandwidth is enhanced to 18.42%...

  7. Antenna design considerations for MIMO TV white-space handsets

    DEFF Research Database (Denmark)

    Tsakalaki, Elpiniki; Alrabadi, Osama; De Carvalho, Elisabeth; Pedersen, Gert Frølund

    The trend in wireless communication is to provide high-speed services utilizing MIMO antenna systems. Moreover, cognitive radio (CR) technology targets to exploit the so-called TV white space (TVWS) utilizing tunable antennas operating over vacant TV bands. The joint requirements for cognition and...... presents a promising approach that empowers the TVWS device with CR-MIMO capabilities under modern smartphone size constraints. The idea is to aggregate a pair of antennas per communication port for a) providing attractive bandwidth properties across the desired TV bands and b) isolating the communication...

  8. A NON-OVERLAPPED PRINTED MONOPOLE ANTENNA FOR UWB APPLICATIONS

    OpenAIRE

    ABDELHADI ASSIR; ABDELMAJID OUMNAD

    2011-01-01

    In this paper, a novel small ultra-wideband (UWB) printed monopole antenna, designed to operate in 3.1-10.6 GHz frequency band, is presented. The antenna is composed of five non-overlapped rectangular patches, a partial ground plane and a standard 50-Ω microstrip feed line. The overall size of the proposed antenna is 22.8 mm  29.5 mm  0.813 mm. The design procedure that we have used is based on a mixed integer genetic algorithm (GA) and the finite-difference time-domain (FDTD) method with u...

  9. Design and development of a small compact ultra wideband antenna

    International Nuclear Information System (INIS)

    In this paper the design of a novel and compact U slot UWB printed monopole microstrip antenna of size 19.2 × 28.8 mm2 has been presented for wireless applications. The planar, small and thin UWB antenna design consists of a U slot radiator fed by a single 50Ω microstrip line with truncated ground plane is excited by a coaxial SMA connector. The simulations are done using the Ansoft High Frequency Structure Simulator (HFSS) software tool. The simulated results of impedance bandwidth are well supported by measurement. The measured group delay and radiation pattern results are also presented and performance of the antenna is analyzed/discussed.

  10. Compact U-Slotted Antenna for Broadband Radar Applications

    Directory of Open Access Journals (Sweden)

    S. Costanzo

    2013-01-01

    Full Text Available The original U-shaped patch antenna is properly modified in this work to provide a compact and broadband antenna configuration with reduced cross-polar effects, well suitable for modern radar applications. The proposed antenna layout is applied to design, realize, and test two different prototypes working at P-band and C-band, typically adopted for ground-penetrating radar. The experimental results successfully demonstrate a large operating bandwidth between 15% and 20%, a significant reduction of size (about half of the standard configuration, and a low cross-polarization level within the operating frequency range.

  11. 96-antenna radioheliograph

    CERN Document Server

    Lesovoi, S V; Ivanov, E F; Gubin, A V

    2014-01-01

    Here we briefly present some design approaches for a multifrequency 96-antenna radioheliograph. The array antenna configuration, transmission lines and digital receivers are the main focus of this work. The radioheliograph is a T-shaped centrally-condensed radiointerferometer operating at the frequency range 4-8~GHz. The justification for the choice of such a configuration is discussed. The antenna signals are transmitted to a workroom by analog optical links. The dynamic range and phase errors of the microwave-over-optical signal are considered. The signals after downconverting are processed by the digital receivers for delay tracking and fringe stopping. The required delay tracking step and data rates are considered. Two 3-bit data streams (I and Q) are transmitted to a correlator with the transceivers embedded in FPGA (Field Programmed Gate Array) chips and with PCI Express cables.

  12. Localisation of chlorophyll within the chloroplast

    NARCIS (Netherlands)

    Thomas, J.B.; Post, L.C.; Vertregt, N.

    1954-01-01

    Silver nitrate reduction was shown to occur in illuminated suspensions of Hibiscus grana. The action spectrum of this reduction, the reaction, proved to coincide satisfactorily with the chlorophyll absorption spectrum. Electron micrographs reveal that this reaction occurs in single lamellae. From

  13. Thin Layer Chromatography (TLC) of Chlorophyll Pigments.

    Science.gov (United States)

    Foote, Jerry

    1984-01-01

    Background information, list of materials needed, procedures used, and discussion of typical results are provided for an experiment on the thin layer chromatography of chlorophyll pigments. The experiment works well in high school, since the chemicals used are the same as those used in paper chromatography of plant pigments. (JN)

  14. Phytoplankton productivity quantified from chlorophyll fluorescence

    DEFF Research Database (Denmark)

    Hancke, Kasper; Dalsgaard, Tage; Sejr, Mikael Kristian;

    Phytoplankton are the main food source for marine life, and accurate uantification of its productivity is essential for understanding how marine food webs function. As a novel non-invasive technology, chlorophyll fluorescence can be used to assess in situ primary production in phytoplankton...

  15. Backfire antennas with dipole elements

    DEFF Research Database (Denmark)

    Nielsen, Erik Dragø; Pontoppidan, Knud

    1970-01-01

    A method is set up for a theoretical investigation of arbitrary backfire antennas based upon dipole structures. The mutual impedance between the dipole elements of the antenna is taken into account, and the field radiated due to a surface wave reflector of finite extent is determined by calculating...... the surface current distribution on the reflector plate. Numerical results obtained for Yagi backfire antennas and short-backfire antennas using this theory are compared with experimental results....

  16. Galileo satellite antenna modeling

    Science.gov (United States)

    Steigenberger, Peter; Dach, Rolf; Prange, Lars; Montenbruck, Oliver

    2015-04-01

    The space segment of the European satellite navigation system Galileo currently consists of six satellites. Four of them belong to the first generation of In-Orbit Validation (IOV) satellites whereas the other two are Full Operational Capability (FOC) satellites. High-precision geodetic applications require detailed knowledge about the actual phase center of the satellite and receiver antenna. The deviation of this actual phase center from a well-defined reference point is described by phase center offsets (PCOs) and phase center variations (PCVs). Unfortunately, no public information is available about the Galileo satellite antenna PCOs and PCVs, neither for the IOV, nor the FOC satellites. Therefore, conventional values for the IOV satellite antenna PCOs have been adopted for the Multi-GNSS experiment (MGEX) of the International GNSS Service (IGS). The effect of the PCVs is currently neglected and no PCOs for the FOC satellites are available yet. To overcome this deficiency in GNSS observation modeling, satellite antenna PCOs and PCVs are estimated for the Galileo IOV satellites based on global GNSS tracking data of the MGEX network and additional stations of the legacy IGS network. Two completely independent solutions are computed with the Bernese and Napeos software packages. The PCO and PCV values of the individual satellites are analyzed and the availability of two different solutions allows for an accuracy assessment. The FOC satellites are built by a different manufacturer and are also equipped with another type of antenna panel compared to the IOV satellites. Signal transmission of the first FOC satellite has started in December 2014 and activation of the second satellite is expected for early 2015. Based on the available observations PCO estimates and, optionally PCVs of the FOC satellites will be presented as well. Finally, the impact of the new antenna model on the precision and accuracy of the Galileo orbit determination is analyzed.

  17. MANUFACTURE OF PHOTOVOLTAIC SOLAR CELL USING PLANT CHLOROPHYLL

    Science.gov (United States)

    To date, we have successfully manufactured working chlorophyll sensitized solar cells using chlorophyll (and b mixture) from spinach leaves. We have evaluated the electronic characteristics (voltage, current, and power outputs using different loading resistors) of this solar c...

  18. Printed MIMO antenna engineering

    CERN Document Server

    Sharawi, Mohammad S

    2014-01-01

    Wireless communications has made a huge leap during the past two decades. The multiple-input-multiple-output (MIMO) technology was proposed in the 1990's as a viable solution that can overcome the data rate limit experienced by single-input-single-output (SISO) systems. This resource is focused on printed MIMO antenna system design. Printed antennas are widely used in mobile and handheld terminals due to their conformity with the device, low cost, good integration within the device elements and mechanical parts, as well as ease of fabrication.A perfect design companion for practicing engineers

  19. Antennas fundamentals, design, measurement

    CERN Document Server

    Long, Maurice

    2009-01-01

    This comprehensive revision (3rd Edition) is a senior undergraduate or first-year graduate level textbook on antenna fundamentals, design, performance analysis, and measurements. In addition to its use as a formal course textbook, the book's pragmatic style and emphasis on the fundamentals make it especially useful to engineering professionals who need to grasp the essence of the subject quickly but without being mired in unnecessary detail. This new edition was prepared for a first year graduate course at Southern Polytechnic State University in Georgia. It provides broad coverage of antenna

  20. The Antennae Galaxies

    OpenAIRE

    Karl, Simon

    2012-01-01

    The Antennae galaxies (NGC 4038/39) are the nearest and best-studied major merger of two gas-rich spirals in the local Universe. They are named after the characteristic pair of tidal tails that protrude out of their main galactic disks. Due to their proximity the Antennae are extremely well sampled by modern high-resolution observations over an enormous wavelength range, from radio to X-ray. This allows for a comprehensive multiwavelength approach to the present-day morpholo...

  1. DSN Microwave Antenna Holography

    Science.gov (United States)

    Rochblatt, D. J.; Seidel, B. L.

    1984-01-01

    The DSN microwave antenna holography project will obtain three-dimensional pictures of the large DSN antenna surfaces. These pictures must be of suffi icient resolution to allow adjustment of the reflector panels to an rms surface of 0.5 mm (0.25 mm, goal). The major parameters and equations needed to define a holographic measurement system are outlined and then the proof of concept demonstration measurement that was made at DSS-43 (Australia) that resulted in contour maps with spatial resolution of 7 m in the aperture plane and resolution orthogonal to the aperture plane of 0.7 mm was discussed.

  2. Hyperbolic thermal antenna

    CERN Document Server

    Barbillon, Grégory; Biehs, Svend-Age; Ben-Abdallah, Philippe

    2016-01-01

    A thermal antenna is an electromagnetic source which emits in its surrounding, a spatially coherent field in the infrared frequency range. Usually, its emission pattern changes with the wavelength so that the heat flux it radiates is weakly directive. Here, we show that a class of hyperbolic materials, possesses a Brewster angle which is weakly dependent on the wavelength, so that they can radiate like a true thermal antenna with a highly directional heat flux. The realization of these sources could open a new avenue in the field of thermal management in far-field regime.

  3. Antennas on circular cylinders

    DEFF Research Database (Denmark)

    Knudsen, H. L.

    1959-01-01

    antenna in a circular cylinder. By a procedure similar to the one used by Silver and Saunders, expressions have been derived for the field radiated from an arbitrary surface current distribution on a cylinder surface coaxial with a perfectly conducting cylinder. The cases where the space between the two...... cylindrical surfaces have the sane characteristic constants and different constants are treated separately. Extensive numerical computations of the field radiated from the slot antennas described here are being carried out, but no numerical results are yet available...

  4. Wireless Distributed Antenna MIMO

    DEFF Research Database (Denmark)

    2015-01-01

    The present disclosure relates to system applications of multicore optical fibers. One embodiment relates to a base transceiver station for a wireless telecommunication system comprising a plurality of antenna units arranged in a MIMO configuration and adapted for transmission and/or reception of...... radio-frequency signals, an optical transmitter in the form of an electro-optic conversion unit for each of said plurality of antenna units, each electro-optic conversion unit adapted for converting an RF signal into an optical signal, a plurality of a single core optical fibers for guiding the optical...

  5. Non-standard antennas

    CERN Document Server

    Le Chevalier, Francois; Staraj, Robert

    2013-01-01

    This book aims at describing the wide variety of new technologies and concepts of non-standard antenna systems - reconfigurable, integrated, terahertz, deformable, ultra-wideband, using metamaterials, or MEMS,  etc, and how they open the way to a wide range of applications, from personal security and communications to multifunction radars and towed sonars, or satellite navigation systems, with space-time diversity on transmit and receive. A reference book for designers  in this lively scientific community linking antenna experts and signal processing engineers.

  6. Antenna Systems for NUTS

    OpenAIRE

    Marholm, Sigvald

    2012-01-01

    NTNU is aiming to build and launch a small student satellite compliant with thedouble CubeSat standard, by 2014. The NTNU Test Satellite (NUTS) will carrytwo radio tranceivers and a beacon transmitter, all located in the VHF and UHFamateur bands. The goal of this thesis was to build the whole antenna systems forthe spacecraft.Turnstile antennas were chosen both for UHF and VHF, since they yield thehighest received signal strength on ground throughout the whole pass of the satel-lite. In order...

  7. Square Planar Monopole Antenna

    OpenAIRE

    Ammann, Max

    1999-01-01

    A planar monopole may be realised by replacing the wire element of a conventional monopole with a planar element. In this case, the planar element which is square, is located above a groundplane and fed using an SMA connector as illustrated. The square monopole has a simple geometry and a smaller bandwidth compared to the circular-disc monopole. However, it is still a broadband antenna with a typical impedance bandwidth of 75 % at S band. This broadband antenna shows a constant radiation patt...

  8. A century of antenna development

    Science.gov (United States)

    Olver, A. D.

    The paper describes a century of antenna development as part of a century of radio communications. This historical review examines, chronologically, the pre-Hertz period, Hertz antennas, the microwave optics period, the Marconi era, short waves, theoretical design before and after computers, and radar. Consideration is also given to mobile antennas, microwave comunications, radio astronomy, and satellite comunications.

  9. China's Largest Radio Antenna System

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    @@ After three-and-half-year efforts, the National Astronomical Observatories at CAS (NAOC) has constructed two arrays of radio antennae: a 50m antenna at Miyun Station in Beijing and a 40m antenna in Kunming, capital of southwest China's Yunnan Province.

  10. Design of Miniaturized Dual-Band Microstrip Antenna for WLAN Application.

    Science.gov (United States)

    Yang, Jiachen; Wang, Huanling; Lv, Zhihan; Wang, Huihui

    2016-01-01

    Wireless local area network (WLAN) is a technology that combines computer network with wireless communication technology. The 2.4 GHz and 5 GHz frequency bands in the Industrial Scientific Medical (ISM) band can be used in the WLAN environment. Because of the development of wireless communication technology and the use of the frequency bands without the need for authorization, the application of WLAN is becoming more and more extensive. As the key part of the WLAN system, the antenna must also be adapted to the development of WLAN communication technology. This paper designs two new dual-frequency microstrip antennas with the use of electromagnetic simulation software-High Frequency Structure Simulator (HFSS). The two antennas adopt ordinary FR4 material as a dielectric substrate, with the advantages of low cost and small size. The first antenna adopts microstrip line feeding, and the antenna radiation patch is composed of a folded T-shaped radiating dipole which reduces the antenna size, and two symmetrical rectangular patches located on both sides of the T-shaped radiating patch. The second antenna is a microstrip patch antenna fed by coaxial line, and the size of the antenna is diminished by opening a stepped groove on the two edges of the patch and a folded slot inside the patch. Simulation experiments prove that the two designed antennas have a higher gain and a favourable transmission characteristic in the working frequency range, which is in accordance with the requirements of WLAN communication. PMID:27355954

  11. Chlorophyll in tomato seeds: marker for seed performance?

    OpenAIRE

    Suhartanto, M.R.

    2002-01-01

    Using Xe-PAM, laser induced fluorometry and high performance liquid chromatography we found that chlorophyll was present in young tomato (cv. Moneymaker) seeds and was degraded during maturation. Fluorescence microscopy and imaging showed that the majority of chlorophyll is located in the seed coat but low levels of chlorophyll were also detected in the embryo, mainly in the radicle tip. Seed chlorophyll fluorescence appeared to be a sensitive indicator of physiological maturity of tomato see...

  12. Vector potential analysis of the helicon antenna in vacuum

    OpenAIRE

    Johnson, Robert W.

    2011-01-01

    The helicon antenna is a well-known device in the field of electric propulsion. Here we investigate the vector potential produced in vacuum by such an antenna with typical size parameters. Both a static and a dynamic analysis are performed. The dynamic calculation is evaluated at both the usual operating frequency and one which is slightly greater. At the higher frequency, a pulse of electromagnetic energy is found to propagate along the cylindrical axis in either direction. The possible adap...

  13. Antenna Beam Pattern Modulation with Lattice Reduction Aided Detection

    OpenAIRE

    Ramirez-Gutierrez, R; Zhang, LX; Elmirghani, J

    2015-01-01

    This paper introduces a novel transmission design for antenna beam pattern modulation (ABPM) with a low complexity decoding method. The concept of ABPM was first presented with the optimal maximum likelihood (ML) decoding. However, an ML detector may not be viable for practical systems when the constellation size or the number of antennas is large such as in massive multiple input multiple output (MIMO) systems. Linear detectors, on the other hand, have lower complexity but inferior performan...

  14. Geostationary Antenna for Disturbance-Free Laser Interferometry (GADFLI)

    OpenAIRE

    McWilliams, Sean T.

    2011-01-01

    We present a mission concept, the Geostationary Antenna for Disturbance-Free Laser Interferometry (GADFLI), for a space-based gravitational-wave interferometer consisting of three satellites in geostationary orbit around the Earth. Compared to the nominal design of the Laser Interferometer Space Antenna (LISA), this concept has the advantages of significantly decreased requirements on the telescope size and laser power, decreased launch mass, substantially improved shot noise resulting from t...

  15. Integrated After-Market Solar Panel Antennas for Small Satellites

    OpenAIRE

    Turpin, Timothy; Mahmoud, Mahmoud; Baktur, Reyhan; Furse, Cynthia

    2009-01-01

    The majority of surface area on a small satellite is taken up by solar panels for power. Integrating antennas with solar panels, would save a valuable amount of satellite surface area, and thus directly contribute to the size reduction and multi-functionality of solar panel. Furthermore, such integration does not require deployed mechanism and therefore is cost-friendly design.Two types of integrations are presented in this paper. The first type is to place optically transparent antennas dire...

  16. On Improving the Performance of Nonphotochemical Quenching in CP29 Light-Harvesting Antenna Complex

    OpenAIRE

    Berman, Gennady P.; Nesterov, Alexander I; Sayre, Richard T.; Still, Susanne

    2015-01-01

    We model and simulate the performance of charge-transfer in nonphotochemical quenching (NPQ) in the CP29 light-harvesting antenna-complex associated with photosystem II (PSII). The model consists of five discrete excitonic energy states and two sinks, responsible for the potentially damaging processes and charge-transfer channels, respectively. We demonstrate that by varying (i) the parameters of the chlorophyll-based dimer, (ii) the resonant properties of the protein-solvent environment inte...

  17. Planar Microstrip Slot Antenna for S and C band Wireless Applications

    International Nuclear Information System (INIS)

    In this paper, compact planar microstrip antennas comprising of broad slots for enhancing various antenna parameters are discussed and presented. The proposed microstrip slot antennas achieved a compactness of maximum 58 % with a peak gain of 7.58 dB. These antennas can be operated for S band applications such as WiMax, operating in the frequency range of 3.3 – 3.6 GHz, RADAR, WLAN, fixed satellite services and maritime mobile services etc. covering 2 – 6 GHz frequency range. The antennas can be used as a compact antenna system where limited size is a foremost requirement. Results also show the satisfactory performance with the dual band frequency characteristics. Details of the antenna design structure, results of return loss (RL), impedance bandwidth and radiation pattern with co-cross polarization are also given.

  18. N Design of an H-shaped Slot Multi-frequency Microstrip Antenna

    Institute of Scientific and Technical Information of China (English)

    YANG Hong; MOU Hong-jiang

    2014-01-01

    Conventional slot microstrip antenna is analyzed, an h-shaped multi-frequency and miniaturization slot microstrip antenna is proposed. Numerical simulation is performed for the characteristics of the antenna with the software HFSS11.0, which is a kind of simulation software based on Finite Element Method, the simulation results shown that the antenna operated at 2.26~2.42GHz, 2.67~2.82GHz , 4.28~4.39GHz and 5.76~5.89GHz when the return loss S1 <-10dB, the size reduced compare to general microstrip antenna, demonstrated the effectiveness of the design scheme. The antenna structure is simple and easily to be implemented, met the wireless LAN 802.11a/b/g/n mobile terminal antenna miniaturization and multi-band requirements.

  19. Is It Possible to Distinguish Between Dust and Salt Aerosol Over Waters with Unknown Chlorophyll Concentrations Using Spectral Remote Sensing?

    Science.gov (United States)

    Levy, R. C.; Kaufman, Y. J.

    1999-01-01

    Atmospheric aerosol has uncertain impacts on the global climate system, as well as on atmospheric and bio-geo-chemical processes of regional and local scales. EOS-MODIS is one example of a satellite sensor designed to improve understanding of the aerosols' type, size and distribution at all temporal and spatial scales. Ocean scientists also plan to use data from EOS-MODIS to assess the temporal and spatial coverage of in-water chlorophyll. MODIS is the first sensor planned to observe the combined ocean-atmosphere system with a wide spectral range (from 410 to 2200 nm). Dust aerosol and salt aerosol have similar spectral signals for wavelengths longer than 550 nm, but because dust selectively absorbs blue light, they have divergent signals in the blue wavelength regions (412 to 490 nm). Chlorophyll also selectively absorbs blue radiation, so that varying chlorophyll concentrations produces a highly varying signal in the blue regions, but less variability in the green, and almost no signal in the red to mid-infrared regions. Thus, theoretically, it may be difficult to differentiate dust and salt in the presence of unknown chlorophyll in the ocean. This study attempts to address the cases in which aerosol and chlorophyll signals can and cannot be separated. For the aerosol spectra, we use the aerosol lookup table from the operational MODIS aerosol-over-ocean algorithm, and for chlorophyll spectra, we use the SeaBAM data set (created for SeaWiFS). We compare the signals using Principal Component Analysis and attempt to retrieve both chlorophyll and aerosol properties using a variant of the operational MODIS aerosol-over-ocean algorithm. Results show that for small optical depths, less than 0.5, it is not possible to differentiate between dust and salt and to determine the chlorophyll concentration at the same time. For larger aerosol optical depths, the chlorophyll signals are comparatively insignificant, and we can hope to distinguish between dust and salt.

  20. Bleaching of chlorophylls by UV irradiation in vitro: the effects on chlorophyll organization in acetone and n-hexane

    OpenAIRE

    JELENA ZVEZDANOVIC; DEJAN MARKOVIC

    2008-01-01

    The stability of chlorophylls toward UV irradiation was studied by Vis spectrophotometry in extracts containing mixtures of photosynthetic pigments in acetone and n-hexane. The chlorophylls underwent destruction (bleaching) obeying first-order kinetics. The bleaching was governed by three major factors: the energy input of the UV photons, the concentration of the chlorophylls and the polarity of the solvent, implying different molecular organizations of the chlorophylls in the two solvents.

  1. MEMS Tunable Antennas

    DEFF Research Database (Denmark)

    Barrio, Samantha Caporal Del; Morris, Art; Pedersen, Gert Frølund

    2014-01-01

    Addressing low frequency bands is challenging on small platforms. Tunability is a promising solution to cover the bandwidth required for 4G mobile communication. The work presents two designs and shows that for comparable efficiency and bandwidth, the tunable antenna occupies half the volume requ...

  2. Frequency scanning microstrip antennas

    DEFF Research Database (Denmark)

    Danielsen, Magnus; Jørgensen, Rolf

    1979-01-01

    The principles of using radiating microstrip resonators as elements in a frequency scanning antenna array are described. The resonators are cascade-coupled. This gives a scan of the main lobe due to the phase-shift in the resonator in addition to that created by the transmission line phase...

  3. Frequency selective lens antenna

    OpenAIRE

    Thornton, J.; Haines, P.

    2007-01-01

    A variant of the hemispherical microwave lens antenna is reported where the ground plane region is modified through use of a frequency selective surface. This allows discrimination of frequencies by two closely spaced primary feeds. A scale model is reported operating at 12 and 30 GHz.

  4. Community Antenna Television (CATV).

    Science.gov (United States)

    Federal Communications Commission, Washington, DC.

    The number of households hooked up to cable television or community antenna television (CATV) is expanding rapidly, and Federal Communications Commission (FCC) has been developing regulations since 1962 to guide the growth of the industry. By 1965 the FCC had claimed jurisdiction over all CATV systems in the U. S. This jurisdiction was challenged…

  5. Evolutionary optimization of optical antennas

    CERN Document Server

    Feichtner, Thorsten; Kiunke, Markus; Hecht, Bert

    2012-01-01

    The design of nano-antennas is so far mainly inspired by radio-frequency technology. However, material properties and experimental settings need to be reconsidered at optical frequencies, which entails the need for alternative optimal antenna designs. Here a checkerboard-type, initially random array of gold cubes is subjected to evolutionary optimization. To illustrate the power of the approach we demonstrate that by optimizing the near-field intensity enhancement the evolutionary algorithm finds a new antenna geometry, essentially a split-ring/two-wire antenna hybrid which surpasses by far the performance of a conventional gap antenna by shifting the n=1 split-ring resonance into the optical regime.

  6. Antenna theory analysis and design

    CERN Document Server

    Balanis, Constantine A

    2005-01-01

    The discipline of antenna theory has experienced vast technological changes. In response, Constantine Balanis has updated his classic text, Antenna Theory, offering the most recent look at all the necessary topics. New material includes smart antennas and fractal antennas, along with the latest applications in wireless communications. Multimedia material on an accompanying CD presents PowerPoint viewgraphs of lecture notes, interactive review questions, Java animations and applets, and MATLAB features. Like the previous editions, Antenna Theory, Third Edition meets the needs of e

  7. IFA and PIFA Size Reduction by Using a Stub Loading

    Directory of Open Access Journals (Sweden)

    Jose Alfredo Tirado-Mendez

    2013-01-01

    Full Text Available A proposed technique for size reduction of a conventional inverted-F antenna (IFA and a planar inverted-F antenna (PIFA by employing a reactive load generated by a short-circuited stub is presented. The reduction factor of both antennas is around 30%, and the main parameters of the devices are preserved, including a fractional bandwidth of 4% and a gain of −2 dB. Both antennas operate around 1.5 GHz.

  8. IFA and PIFA Size Reduction by Using a Stub Loading

    OpenAIRE

    Jose Alfredo Tirado-Mendez; Rene Acevo-Herrera; Ruben Flores-Leal; Roberto Linares-Miranda; Hildeberto Jardon-Aguilar

    2013-01-01

    A proposed technique for size reduction of a conventional inverted-F antenna (IFA) and a planar inverted-F antenna (PIFA) by employing a reactive load generated by a short-circuited stub is presented. The reduction factor of both antennas is around 30%, and the main parameters of the devices are preserved, including a fractional bandwidth of 4% and a gain of −2 dB. Both antennas operate around 1.5 GHz.

  9. Chlorophyll 'a' and particulate organic carbon in relation to some physico-chemical parameters along southwest coast of India

    Digital Repository Service at National Institute of Oceanography (India)

    Devi, K.S.; Balasubramanian, T.; Jayalakshmy, K.V.; Balachandran, K.K.; Sankaranarayanan, V.N.

    ' and environmental parameters except NO sub(2)-N varied spatially, while POC and NO sub(2)-N diurnally. For total and 60 mu m size fractioned chlorophyll 'a' a negative relation of high gradient with salinity while, for 20 mu m size fraction a positive relation...

  10. Rhombic Split Ring Resonator (R-SRR Structure on Rectangular Patch Antenna Design

    Directory of Open Access Journals (Sweden)

    H. Nornikman

    2013-01-01

    Full Text Available This work focusing on the effect of the complementary rhombic split ring resonator (R-SRR structure of gain, return loss and the radiation pattern the rectangular patch antenna design. The basic rectangular patch antenna design had been simulated in CST Microwave Studio simulation software. Then, the single unit of the R-SRR had been added into the patch antenna design. The targeting frequency of this antenna is 2.40 GHz for Wireless Local Area Network (WLAN application. Compared with the conventional microstrip patch antenna with the same aperture size, the performance gain of the patch antennas is improved obviously and suitable for targeting frequency of 2.40 GHz. The parametric studies done this work work are the different variation pattern of R-SRR, different distance between two RSRR structure and different size of R-SRR.

  11. Triband Compact Antenna for Multistandard Terminals and User's Hand Effect

    Directory of Open Access Journals (Sweden)

    M. Koubeissi

    2009-01-01

    Full Text Available A novel compact wideband triband antenna for mobile terminals based on PIFA element is proposed. The antenna operates at the following frequency bands: Wireless-LAN 802.11 b, g, a and WiMAX 3.5 GHz. The antenna was studied by means of numerical simulations as well as the ground plane dimensions and user's hand effects. The overall size of the radiating element which is 1.8×1.54×9 mm makes it suitable for use in terminals and appropriate to integrated as an internal laptop antenna. The measured bandwidths show that the proposed antenna can cover three bands (2.39–2.48 GHz, (3.36–3.76 GHz, and (4.7–6.3 GHz and the total efficiency is better than 90%. The radiation patterns of the antenna were carried in an anechoic chamber and are given to demonstrate the antenna's performance.

  12. Evolutionary Optimization of Quadrifilar Helical and Yagi-Uda Antennas

    Science.gov (United States)

    Lohn, Jason D.; Kraus, William F.; Linden, Derek S.; Stoica, Adrian; Clancy, Daniel (Technical Monitor)

    2002-01-01

    We present optimization results obtained for two type of antennas using evolutionary algorithms. A quadrifilar helical UHF antenna is currently flying aboard NASA's Mars Odyssey spacecraft and is due to reach final Martian orbit insertion in January, 2002. Using this antenna as a benchmark, we ran experiments employing a coevolutionary genetic algorithm to evolve a quadrifilar helical design in-situ - i.e., in the presence of a surrounding structure. Results show a 93% improvement at 400 MHz and a 48% improvement at 438 MHz in the average gain. The evolved antenna is also one-fourth the size. Yagi-Uda antennas are known to be difficult to design and optimize due to their sensitivity at high gain and the inclusion of numerous parasitic elements. Our fitness calculation allows the implicit relationship between power gain and sidelobe/backlobe loss to emerge naturally, a technique that is less complex than previous approaches. Our results include Yagi-Uda antennas that have excellent bandwidth and gain properties with very good impedance characteristics. Results exceeded previous Yagi-Uda antennas produced via evolutionary algorithms by at least 7.8% in mainlobe gain.

  13. A New Fractal-Based Miniaturized Dual Band Patch Antenna for RF Energy Harvesting

    Directory of Open Access Journals (Sweden)

    Sika Shrestha

    2014-01-01

    Full Text Available The growth of wireless communications in recent years has made it necessary to develop compact, lightweight multiband antennas. Compact antennas can achieve the same performance as large antennas do with low price and with greater system integration. Dual-frequency microstrip antennas for transmission and reception represent promising approach for doubling the system capacity. In this work, a miniaturized dual band antenna operable at 2.45 and 5.8 GHz is constructed by modifying the standard microstrip patch antenna geometry into a fractal structure. In addition to miniaturization and dual band nature, the proposed antenna also removes unwanted harmonics without the use of additional filter component. Using a finite-element-method-based high frequency structure simulator (HFSS, the antenna is designed and its performance in terms of return loss, impedance matching, radiation pattern, and voltage standing wave ratio (VSWR is demonstrated. Simulation results are shown to be in close agreement with performance measurements from an actual antenna fabricated on an FR4 substrate. The proposed antenna can be integrated with a rectifier circuit to develop a compact rectenna that can harvest RF energy in both of these frequency bands at a reduction in size of 25.98% relative to a conventional rectangular patch antenna.

  14. Fractal structures in casting films from chlorophyll

    Science.gov (United States)

    Pedro, G. C.; Gorza, F. D. S.; de Souza, N. C.; Silva, J. R.

    2014-04-01

    Chlorophyll (Chl) molecules are important because they can act as natural light-harvesting devices during the photosynthesis. In addition, they have potential for application as component of solar cell. In this work, we have prepared casting films from chlorophyll (Chl) and demonstrated the occurrence of fractal structures when the films were submitted to different concentrations. By using optical microscopy and the box-count method, we have found that the fractal dimension is Df = 1.55. This value is close to predicted by the diffusion-limited aggregation (DLA) model. This suggests that the major mechanism - which determines the growth of the fractal structures from Chl molecules - is the molecular diffusion. Since the efficiencies of solar cells depend on the morphology of their interfaces, these finds can be useful to improve this kind of device.

  15. Genetic analysis of sunflower chlorophyll mutants

    International Nuclear Information System (INIS)

    The method of getting the chlorophyll mutations in sunflower was developed by Y.D. Beletskii in 1969 with the use of N-nitroso-N-methylurea (NMH). Certain concentrations of NMH are known to induce plastid mutations in growing seeds, and their yield depends on the duration of the exposure. The given work presented studies on the influence of rifampicin (R) and 2,4-dinitrophenol (DNP) on the genetic activity NMH, as an inductor of plastid and nuclear mutations

  16. Extraction of Chlorophyll from Alfalfa Plant

    OpenAIRE

    Ali Khalid Khudair Al-Jomaily; Ahmed Jawad; Isam Kamal

    2006-01-01

    The extraction process of chlorophyll from dehydrated and pulverized alfalfa plant were studied by percolation method. Two solvent systems were used for the extraction namely; Ethanol-water and Hexane-Toluene systems . The effect of circulation rate, solvent concentration, and solvent volume to solid weight ratio were studied. In both ethanol water, and Hexane-Toluene systems it appears that solvent concentration is the most effective variable.

  17. Extraction of Chlorophyll from Alfalfa Plant

    Directory of Open Access Journals (Sweden)

    Ali Khalid Khudair Al-Jomaily

    2006-01-01

    Full Text Available The extraction process of chlorophyll from dehydrated and pulverized alfalfa plant were studied by percolation method. Two solvent systems were used for the extraction namely; Ethanol-water and Hexane-Toluene systems . The effect of circulation rate, solvent concentration, and solvent volume to solid weight ratio were studied. In both ethanol water, and Hexane-Toluene systems it appears that solvent concentration is the most effective variable.

  18. Chlorophyll fluorescence emission spectrum inside a leaf

    OpenAIRE

    Pedrós Esteban, Roberto; Moya, Ismael; Goulas, Yves; Jacquemoud, Stéphane

    2008-01-01

    Chlorophyll a fluorescence can be used as an early stress indicator. Fluorescence is also connected to photosynthesis so it can be proposed for global monitoring of vegetation status from a satellite platform. Nevertheless, the correct interpretation of fluorescence requires accurate physical models. The spectral shape of the leaf fluorescence free of any re-absorption effect plays a key role in the models and is difficult to measure. We present a vegetation fluorescence emission spectrum fre...

  19. Degradation of Chlorophyll Luminescence in Plants

    International Nuclear Information System (INIS)

    The chlorophyll photoluminescence intensity degradation of Vallisneria spiralis L. water plant is studied. It is shown that the degradation curve is rather well described by a sum of two hyperbolic functions. The rate of intensity degradation reduces at low temperatures. At room temperature, a slow restoration of the luminescent system is observed after the irradiation has been ceased. No restoration is detected at the liquid nitrogen temperature. A simplified model which describes the luminescence degradation according to the quadratic law is suggested.

  20. Compact Dual-Band Zeroth-Order Resonance Antenna

    Institute of Scientific and Technical Information of China (English)

    XU He-Xiu; WANG Guang-Ming; GONG Jian-Qiang

    2012-01-01

    A novel microstrip zeroth-order resonator (ZOR) antenna and its equivalent circuit model are exploited with two zeroth-order resonances.It is constructed based on a resonant-type composite right/left handed transmission line (CRLH TL) using a Wunderlich-shaped extended complementary single split ring resonator pair (W-ECSSRRP) and a series capacitive gap.The gap either can be utilized for double negative (DNG) ZOR antenna or be removed to engineer a simplified elision-negative ZOR (ENG) antenna.For verification,a DNG ZOR antenna sample is fabricated and measured.Numerical and experimental results agree well with each other,indicating that the omnidirectional radiations occur at two frequency bands which are accounted for by two shunt branches in the circuit model.The size of the antenna is 49% more compact than its previous counterpart.The superiority of WECSSRRP over CSSRRP lies in the lower fundamental resonance of the antenna by 38.2% and the introduction of a higher zeroth-order resonance.%A novel microstrip zeroth-order resonator (ZOR) antenna and its equivalent circuit model are exploited with two zeroth-order resonances. It is constructed based on a resonant-type composite right/left handed transmission line (CRLH TV) using a Wunderlich-shaped extended complementary single split ring resonator pair (W-ECSSRRP) and a series capacitive gap. The gap either can be utilized for double negative (DNG) ZOR antenna or be removed to engineer a simplified elision-negative ZOR (ENG) antenna. For verification, a DNG ZOR antenna sample is fabricated and measured. Numerical and experimental results agree well with each other, indicating that the omnidirectional radiations occur at two frequency bands which are accounted for by two shunt branches in the circuit model. The size of the antenna is 49% more compact than its previous counterpart. The superiority of W-ECSSRRP over CSSRRP lies in the lower fundamental resonance of the antenna by 38.2% and the introduction of a

  1. Resonant Frequency Calculation and Optimal Design of Peano Fractal Antenna for Partial Discharge Detection

    OpenAIRE

    Jian Li,; Changkui Cheng; Lianwei Bao; Tianyan Jiang

    2012-01-01

    Ultra-high-frequency (UHF) approaches have caught increasing attention recently and have been considered as a promising technology for online monitoring partial discharge (PD) signals. This paper presents a Peano fractal antenna for UHF PD online monitoring of transformer with small size and multiband. The approximate formula for calculating the first resonant frequency of the Peano fractal antenna is presented. The results show that the first resonant frequency of the Peano fractal antenna i...

  2. Experimental Studies of Antenna Miniaturization Using Magneto-Dielectric and Dielectric Materials

    OpenAIRE

    Karilainen, Antti O.; Ikonen, Pekka M. T.; Constantin R. Simovski; Tretyakov, Sergei A.; Lagarkov, Andrey N.; Maklakov, Sergei A.; Rozanov, Konstantin N.; Starostenko, Sergey N.

    2009-01-01

    Measurement results for a meandered planar inverted-F antenna (PIFA) loaded with magneto-dielectric and dielectric materials are presented. Figures of merit and ways to compare antennas with different fillings materials are discussed. The used magneto-dielectric material is described, the radiation mechanism of the meandered PIFA is studied, and the proper position for dielectric and magneto-dielectric filling is discussed and identified. Identical-size antennas with dielectric and magneto-di...

  3. Measurement and Performance of Textile Antenna Efficiency on a Human Body in a Reverberation Chamber

    OpenAIRE

    Boyes, Stephen; Soh, Ping Jack; Huang, Yi; VANDENBOSCH, Guy; Khiabani, Neda

    2013-01-01

    With the advent of on-body communication research in recent years, there is a growing need for antenna developments that satisfy a wide criteria (one being minimal efficiency degradation) in order to be integrated successfully onto human subjects; one promising development is the textile antenna. In this paper we investigate the efficiency performance of some newly designed small sized textile antennas on live human subjects using a reverberation chamber. Firstly, we show that the material se...

  4. Chlorophyll loss associated with heat-induced senescence in bentgrass.

    Science.gov (United States)

    Jespersen, David; Zhang, Jing; Huang, Bingru

    2016-08-01

    Heat stress-induced leaf senescence is characterized by the loss of chlorophyll from leaf tissues. The objectives of this study were to examine genetic variations in the level of heat-induced leaf senescence in hybrids of colonial (Agrostis capillaris)×creeping bentgrass (Agrostis stolonifera) contrasting in heat tolerance, and determine whether loss of leaf chlorophyll during heat-induced leaf senescence was due to suppressed chlorophyll synthesis and/or accelerated chlorophyll degradation in the cool-season perennial grass species. Plants of two hybrid backcross genotypes ('ColxCB169' and 'ColxCB190') were exposed to heat stress (38/33°C, day/night) for 28 d in growth chambers. The analysis of turf quality, membrane stability, photochemical efficiency, and chlorophyll content demonstrated significant variations in the level of leaf senescence induced by heat stress between the two genotypes, with ColXCB169 exhibiting a lesser degree of decline in chlorophyll content, photochemical efficiency and membrane stability than ColXCB190. The assays of enzymatic activity or gene expression of several major chlorophyll-synthesizing (porphobilinogen deaminase, Mg-chelatase, protochlorophyllide-reductase) and chlorophyll-degrading enzymes (chlorophyllase, pheophytinase, and chlorophyll-degrading peroxidase) indicated heat-induced decline in leaf chlorophyll content was mainly due to accelerated chlorophyll degradation, as manifested by increased gene expression levels of chlorophyllase and pheophytinase, and the activity of pheophytinase (PPH), while chlorophyll-synthesizing genes and enzymatic activities were not differentially altered by heat stress in the two genotypes. The analysis of heat-induced leaf senescence of pph mutants of Arabidopsis further confirmed that PPH could be one enzymes that plays key roles in regulating heat-accelerated chlorophyll degradation. Further research on enzymes responsible in part for the loss of chlorophyll during heat

  5. Understanding and optimizing microstrip patch antenna cross polarization radiation on element level for demanding phased array antennas in weather radar applications

    Science.gov (United States)

    Vollbracht, D.

    2015-11-01

    The antenna cross polarization suppression (CPS) is of significant importance for the accurate calculation of polarimetric weather radar moments. State-of-the-art reflector antennas fulfill these requirements, but phased array antennas are changing their CPS during the main beam shift, off-broadside direction. Since the cross polarization (x-pol) of the array pattern is affected by the x-pol element factor, the single antenna element should be designed for maximum CPS, not only at broadside, but also for the complete angular electronic scan (e-scan) range of the phased array antenna main beam positions. Different methods for reducing the x-pol radiation from microstrip patch antenna elements, available from literature sources, are discussed and summarized. The potential x-pol sources from probe fed microstrip patch antennas are investigated. Due to the lack of literature references, circular and square shaped X-Band radiators are compared in their x-pol performance and the microstrip patch antenna size variation was analyzed for improved x-pol pattern. Furthermore, the most promising technique for the reduction of x-pol radiation, namely "differential feeding with two RF signals 180° out of phase", is compared to single fed patch antennas and thoroughly investigated for phased array applications with simulation results from CST MICROWAVE STUDIO (CST MWS). A new explanation for the excellent port isolation of dual linear polarized and differential fed patch antennas is given graphically. The antenna radiation pattern from single fed and differential fed microstrip patch antennas are analyzed and the shapes of the x-pol patterns are discussed with the well-known cavity model. Moreover, two new visual based electromagnetic approaches for the explanation of the x-pol generation will be given: the field line approach and the surface current distribution approach provide new insight in understanding the generation of x-pol component in microstrip patch antenna radiation

  6. Evaluating the relationship between leaf chlorophyll concentration and SPAD-502 chlorophyll meter readings.

    Science.gov (United States)

    Uddling, J; Gelang-Alfredsson, J; Piikki, K; Pleijel, H

    2007-01-01

    Relationships between chlorophyll concentration ([chl]) and SPAD values were determined for birch, wheat, and potato. For all three species, the relationships were non-linear with an increasing slope with increasing SPAD. The relationships for birch and wheat were strong (r (2) approximately 0.9), while the potato relationship was comparatively weak (r (2) approximately 0.5). Birch and wheat had very similar relationships when the chlorophyll concentration was expressed per unit leaf area, but diverged when it was expressed per unit fresh weight. Furthermore, wheat showed similar SPAD-[chl] relationships for two different cultivars and during two different growing seasons. The curvilinear shape of the SPAD-[chl] relationships agreed well with the simulated effects of non-uniform chlorophyll distribution across the leaf surface and multiple scattering, causing deviations from linearity in the high and low SPAD range, respectively. The effect of non-uniformly distributed chlorophyll is likely to be more important in explaining the non-linearity in the empirical relationships, since the effect of scattering was predicted to be comparatively weak. The simulations were based on the algorithm for the calculation of SPAD-502 output values. We suggest that SPAD calibration curves should generally be parameterised as non-linear equations, and we hope that the relationships between [chl] and SPAD and the simulations of the present study can facilitate the interpretation of chlorophyll meter calibrations in relation to optical properties of leaves in future studies. PMID:17342446

  7. Quenching of chlorophyll fluorescence induced by silver nanoparticles.

    Science.gov (United States)

    Queiroz, A M; Mezacasa, A V; Graciano, D E; Falco, W F; M'Peko, J-C; Guimarães, F E G; Lawson, T; Colbeck, I; Oliveira, S L; Caires, A R L

    2016-11-01

    The interaction between chlorophyll (Chl) and silver nanoparticles (AgNPs) was evaluated by analyzing the optical behavior of Chl molecules surrounded by different concentrations of AgNPs (10, 60, and 100nm of diameter). UV-Vis absorption, steady state and time-resolved fluorescence measurements were performed for Chl in the presence and absence of these nanoparticles. AgNPs strongly suppressed the Chl fluorescence intensity at 678nm. The Stern-Volmer constant (KSV) showed that fluorescence suppression is driven by the dynamic quenching process. In particular, KSV was nanoparticle size-dependent with an exponential decrease as a function of the nanoparticle diameter. Finally, changes in the Chl fluorescence lifetime in the presence of nanoparticles demonstrated that the fluorescence quenching may be induced by the excited electron transfer from the Chl molecules to the metal nanoparticles. PMID:27280858

  8. Microelectrical Mechanical Systems Switch for Designing Multi-Band Antenna

    Directory of Open Access Journals (Sweden)

    A. H.M.Z. Alam

    2009-01-01

    Full Text Available Problem statement: In this study Microelectrical Mechanical System (MEMS switches were proposed to design a reconfigurable/multi-band antenna to replaced PIN diode switches or semiconductor switches due to lower insertion losses, good isolation, much lower intermodulation distortion, and lower power consumption. The antenna is able to operate at very high frequencies. Approach: A reconfigurable antenna that is capable to operate at several frequencies was proposed by introducing two adjacent patches along with main radiating patch and two MEMS switches. Parametric analysis of the size of the wing patches was done for finding optimum size. A comparative study was done for Alumina, SiN, GaAs and Teflon as MEMS bridge materials for finding better results in terms of return loss and number of bands. The design was performed by using 3D electromagnetic simulator HFSS considering ideal MEMS switches. Results: It was found that SiN as MEMS bridge material makes the antenna to operate at 16.76, 23.56 and 27.7 GHz in the “OFF” states and operate at 20.9 and 21.91 GHz in the “ON” states of MEMS switches. Conclusion/Recommendations: MEMS cantilever beam material played an important role for providing antenna to operate at multi-band frequencies. The proposed multiband/reconfigurable antenna can be implemented with easy fabrication process steps by the Sandwich method of fabrication.

  9. A Wideband Single Fed L Slot Circularly Polarized Antenna

    Directory of Open Access Journals (Sweden)

    Nisha

    2014-05-01

    Full Text Available A single-fed circularly polarized (CP patch antenna is designed and built using L-slot loaded patch technique. The antenna is designed on a high dielectric constant (εr = 10.02 substrate which achieves a reasonable bandwidth and axial ratio bandwidth with respect to a U slot antenna. At the operating frequency of 1.575 GHz with the size of the patch is 25mm X 25mm, while ground plane of 60mm X 60mm and the thickness of the substrate is 9.12mm. Bandwidth is enhanced to 18.42% and Axial Ratio Bandwidth by 4% by this design. The other Parameters of antenna like return loss and radiation pattern are also analyzed using HFSS software.

  10. Design of an UWB Patch Antenna for Dual Frequency Operations

    Directory of Open Access Journals (Sweden)

    M.M. Islam

    2014-01-01

    Full Text Available The purpose of this study is to present the development of an Ultra-Wide Band (UWB patch antenna for dual frequency operations. The size of the proposed antenna is 40×40×1.6 mm3 and is excited by micros trip line. The Finite Element Method (FEM based on high frequency electromagnetic simulation software is used in this investigation. Return loss is obtained below -10 dB from 8.39 to 9.7 GHz. It has achieved stable radiation efficiency 84% with gain 3.81 dB and 4.25 dB in the operating frequency band. The antenna generates two separate resonant frequencies to cover UWB band (3.1-10.6 GHz. Lower resonant mode of the antenna has an impedance bandwidth of 940 MHz (9-8.06 GHz and the upper resonant mode has a bandwidth of 1 GHz (10.08-9.08 GHz.

  11. Surface plasma source with saddle antenna radio frequency plasma generator.

    Science.gov (United States)

    Dudnikov, V; Johnson, R P; Murray, S; Pennisi, T; Piller, C; Santana, M; Stockli, M; Welton, R

    2012-02-01

    A prototype RF H(-) surface plasma source (SPS) with saddle (SA) RF antenna is developed which will provide better power efficiency for high pulsed and average current, higher brightness with longer lifetime and higher reliability. Several versions of new plasma generators with small AlN discharge chambers and different antennas and magnetic field configurations were tested in the plasma source test stand. A prototype SA SPS was installed in the Spallation Neutron Source (SNS) ion source test stand with a larger, normal-sized SNS AlN chamber that achieved unanalyzed peak currents of up to 67 mA with an apparent efficiency up to 1.6 mA∕kW. Control experiments with H(-) beam produced by SNS SPS with internal and external antennas were conducted. A new version of the RF triggering plasma gun has been designed. A saddle antenna SPS with water cooling is fabricated for high duty factor testing. PMID:22380221

  12. Fundamental bounds for harvesting sunlight with aperture antennae

    Science.gov (United States)

    Mashaal, Heylal; Gordon, Jeffrey M.

    2011-10-01

    The tantalizing prospect of using antennae for solar power conversion received preliminary consideration, but was not pursued in earnest due to the daunting challenges in suitable materials, fabrication procedures, and the rectification (conversion to DC power) of frequencies approaching 1 PHz (1015 s-1). Recent advances in nano-materials and nano-fabrication technologies have prompted revisiting the solar antenna strategy. Coherence theory informs us that even ostensibly incoherent radiation is partially coherent on a sufficiently small scale. Based on a generalized broadband analysis, we show how the partial coherence of sunlight, exhibiting transverse partial coherence on a scale of two orders of magnitude larger than its characteristic wavelengths, impacts the potential of harvesting solar energy with aperture antennae (coherent detectors), and establish a fundamental bound. These results quantify the tradeoff between intercepted power and averaged intensity with which the effect of increasing antenna size (and hence greater system simplicity) can be evaluated.

  13. Flexible sixteen monopole antenna array for microwave breast cancer detection.

    Science.gov (United States)

    Bahrami, H; Porter, E; Santorelli, A; Gosselin, B; Popovic, M; Rusch, L A

    2014-01-01

    Radar based microwave imaging (MI) has been widely studied for breast cancer detection in recent times. Sensing dielectric property differences of tissues over a wide frequency band has been made possible by ultra-wideband (UWB) techniques. In this paper, a flexible, compact monopole antenna on a 100 μm Kapton polyimide is designed, using a high frequency structure simulator (HFSS), to be in contact with biological breast tissues over the 2-5GHz frequency range. The antenna parameters are optimized to obtain a good impedance match over the required frequency range. The designed antenna size is 18mm × 18mm. Further, a flexible conformal 4×4 ultra-wideband antenna array, in a format similar to that of a bra, was developed for a radar-based breast cancer detection system. PMID:25570813

  14. A NON-OVERLAPPED PRINTED MONOPOLE ANTENNA FOR UWB APPLICATIONS

    Directory of Open Access Journals (Sweden)

    ABDELHADI ASSIR

    2011-10-01

    Full Text Available In this paper, a novel small ultra-wideband (UWB printed monopole antenna, designed to operate in 3.1-10.6 GHz frequency band, is presented. The antenna is composed of five non-overlapped rectangular patches, a partial ground plane and a standard 50-Ω microstrip feed line. The overall size of the proposed antenna is 22.8 mm  29.5 mm  0.813 mm. The design procedure that we have used is based on a mixed integer genetic algorithm (GA and the finite-difference time-domain (FDTD method with uniaxial perfectly matched layer(UPML absorbing boundary condition. The optimized printed monopole antenna is analyzed using our own FDTD code and the high frequency structure simulator (HFSS.

  15. 10 GHz microstrip spanar antennas: an experimental analysis

    International Nuclear Information System (INIS)

    This paper presents Spanar Antenna designed using CST Microwave Studio Simulation 2011. The proposed antenna was designed to operate at 10 GHz, which suggested return loss, S11 must be less than -10 dB and voltage standing wave ratio (VSWR) must be less than 2. The best performance of simulation of Spanar Antenna was obtained at a small size of 24.8 mm × 8.0 mm with dimension board of FR4 substrate 31.7 mm × 18.5 mm. The thickness (h) and dielectric constant (εr) of substrate were 1.6 mm and 4.7. An analysis between simulation result and measurement result has been compared in order to see the antenna performance.

  16. Minimum Q Electrically Small Spherical Magnetic Dipole Antenna - Practice

    DEFF Research Database (Denmark)

    Kim, Oleksiy S.; Breinbjerg, Olav

    2009-01-01

    Practical aspects of applying a magnetic core to approach the Chu lower bound for the radiation Q factor of an electrically small magnetic dipole antenna are considered. It is shown that although a magnetic core does reduce the Q factor, its effect is not as strong as predicted by Wheeler. This is...... due to the fact that a finite size magnetic core supports multiple internal resonances, which spoil the Q factor also away from exact resonance frequencies; and in a worst case they can even significantly increase Q. The resonances in question are not only those of the TE10 spherical mode, but also...... resonances of all other modes that are not sufficiently suppressed in the antenna. Numerical results for a 4-arm spherical helix antenna filled with magnetic material demonstrate the destroying effect of the parasitic TM11 mode on the antenna Q factor. Theoretical considerations as well as numerical results...

  17. Omnidirectional Circularly Polarized Antennas – a Small Antenna Perspective

    OpenAIRE

    Narbudowicz, Adam; Ammann, Max

    2015-01-01

    The paper discusses recent developments and challenges in the design of small omnidirectionalcircularly-polarized (CP) antennas. Although omnidirectional CP coverage is easily achievable usingantenna arrays, it is just recently that small and low-cost antennas delivered this functionality.The paper addresses practical design problems for these antennas, not reported in previous publications.This includes selection of the omnidirectional plane relative to the ground plane and measurement chall...

  18. Microsecond switchable thermal antenna

    Energy Technology Data Exchange (ETDEWEB)

    Ben-Abdallah, Philippe, E-mail: pba@institutoptique.fr; Benisty, Henri; Besbes, Mondher [Laboratoire Charles Fabry, UMR 8501, Institut d' Optique, CNRS, Université Paris-Sud 11, 2, Avenue Augustin Fresnel, 91127 Palaiseau Cedex (France)

    2014-07-21

    We propose a thermal antenna that can be actively switched on and off at the microsecond scale by means of a phase transition of a metal-insulator material, the vanadium dioxide (VO{sub 2}). This thermal source is made of a periodically patterned tunable VO{sub 2} nanolayer, which support a surface phonon-polariton in the infrared range in their crystalline phase. Using electrodes properly registered with respect to the pattern, the VO{sub 2} phase transition can be locally triggered by ohmic heating so that the surface phonon-polariton can be diffracted by the induced grating, producing a highly directional thermal emission. Conversely, when heating less, the VO{sub 2} layers cool down below the transition temperature, the surface phonon-polariton cannot be diffracted anymore so that thermal emission is inhibited. This switchable antenna could find broad applications in the domain of active thermal coatings or in those of infrared spectroscopy and sensing.

  19. Small inductor Loaded mobile phone Antenna

    DEFF Research Database (Denmark)

    Thaysen, Jesper; Jakobsen, Kaj Bjarne

    2004-01-01

    In this paper a size reduction technique of the Planar Inverted F Antenna (PIFA) is presented. Using an 18 nH lumped inductor in addition to a small 0.3 cm3 PIFA located on a 5 mm thick dielectric foam above a 40 x 100 mm2 ground plane it is possible to reduce the resonant frequency by 33 % for a...... fixed physical size. The measured –6 dB bandwidth is 6.7% with a peak radiation efficiency of 88 %....

  20. 47 CFR 80.863 - Antenna system.

    Science.gov (United States)

    2010-10-01

    ... 47 Telecommunication 5 2010-10-01 2010-10-01 false Antenna system. 80.863 Section 80.863... Antenna system. (a) An antenna system must be installed which is as nondirectional and as efficient as is... construction of the required antenna must insure operation in time of emergency. (b) If the required antenna...

  1. 47 CFR 80.866 - Spare antenna.

    Science.gov (United States)

    2010-10-01

    ... 47 Telecommunication 5 2010-10-01 2010-10-01 false Spare antenna. 80.866 Section 80.866... Spare antenna. A spare transmitting antenna completely assembled for immediate erection must be provided. If the installed transmitting antenna is suspended between supports, this spare antenna must be...

  2. Analysis and design of plasma monopole antenna

    OpenAIRE

    Wei, Li; Jinghui, Qiu; Ying, Suo

    2009-01-01

    Two kinds of plasma monopole antennas are simulated and analyzed in this article. For different radius, reflection coefficient, radiation pattern and radiation efficiency of a cylindrical plasma monopole antenna are calculated respectively. According to actual situation, a conical plasma monopole antenna with different cone angle is simulated. Impedance and radiation characteristics of the plasma antenna are similar to the metal monopole antenna.

  3. Helicopter Rotor Antenna

    Science.gov (United States)

    Pogorzelski, Ronald J.; Cable, Vaughn P.

    2001-01-01

    This effort was directed toward demonstration of the efficacy of a concept for mitigation of the rotor blade modulation problem in helicopter communications. An antenna is envisioned with radiating elements mounted on the rotor and rotating with it. The rf signals are coupled to the radio stationary with respect to the airframe via a coupler of unique design. The coupler has an rf cavity within which a mode is established and the field distribution of this mode is sampled by probes rotating with the radiating elements. In this manner the radiated pattern is "despun" with respect to the rotor. Theoretical analysis has indicated that this arrangement will be less susceptible to rotor blade modulation that would be a conventional fixed mounted antenna. A small coupler operating at S-band was designed, fabricated, and mounted on a mockup representative of a helicopter body. A small electric motor was installed to rotate the rotor portion of the coupler along with a set of radiating elements during testing. This test article was be evaluated using the JPL Mesa Antenna Measurement Facility to establish its ability to mitigate rotor blade modulation. It was found that indeed such a coupler will result in a despun pattern and that such a pattern can be effective in mitigation of rotor blade modulation.

  4. Microstrip antenna theory and design

    Science.gov (United States)

    James, J. R.; Hall, P. S.; Wood, C.

    Microstrip is the name given to a type of open waveguiding structure which is now commonly used in present-day electronics, not only as a transmission line but for circuit components such as filters, couplers, and resonators. The idea of using microstrip to construct antennas is a much more recent development. The purpose of this monograph is to present the reader with an appreciation of useful antenna design approaches and the overall state-of-the art situation. Flat-plate antenna techniques and constraints on performance are considered along with microstrip design equations and data, the radiation mechanism of an open-circuit microstrip termination and the resulting design implications, the basic methods of calculation and design of patch antennas, and linear array techniques. Attention is also given to techniques and design limitations in two-dimensional arrays, circular polarization techniques, manufacturing and operational problems of microstrip antennas, recent advances in microstrip antenna analysis, and possible future developments.

  5. Antenna structure with distributed strip

    Science.gov (United States)

    Rodenbeck, Christopher T.

    2008-03-18

    An antenna comprises electrical conductors arranged to form a radiating element including a folded line configuration and a distributed strip configuration, where the radiating element is in proximity to a ground conductor. The folded line and the distributed strip can be electrically interconnected and substantially coplanar. The ground conductor can be spaced from, and coplanar to, the radiating element, or can alternatively lie in a plane set at an angle to the radiating element. Embodiments of the antenna include conductor patterns formed on a printed wiring board, having a ground plane, spacedly adjacent to and coplanar with the radiating element. Other embodiments of the antenna comprise a ground plane and radiating element on opposed sides of a printed wiring board. Other embodiments of the antenna comprise conductors that can be arranged as free standing "foils". Other embodiments include antennas that are encapsulated into a package containing the antenna.

  6. Antenna Calibration and Measurement Equipment

    Science.gov (United States)

    Rochblatt, David J.; Cortes, Manuel Vazquez

    2012-01-01

    A document describes the Antenna Calibration & Measurement Equipment (ACME) system that will provide the Deep Space Network (DSN) with instrumentation enabling a trained RF engineer at each complex to perform antenna calibration measurements and to generate antenna calibration data. This data includes continuous-scan auto-bore-based data acquisition with all-sky data gathering in support of 4th order pointing model generation requirements. Other data includes antenna subreflector focus, system noise temperature and tipping curves, antenna efficiency, reports system linearity, and instrument calibration. The ACME system design is based on the on-the-fly (OTF) mapping technique and architecture. ACME has contributed to the improved RF performance of the DSN by approximately a factor of two. It improved the pointing performances of the DSN antennas and productivity of its personnel and calibration engineers.

  7. Integrated, Dual Orthogonal Antennas for Polarimetric Ground Penetrating Radar

    Science.gov (United States)

    Pauli, Mario; Wiesbeck, Werner

    2015-04-01

    Ground penetrating radar systems are mostly equipped with single polarized antennas, for example with single linear polarization or with circular polarization. The radiated waves are partly reflected at the ground surface and very often the penetrating waves are distorted in their polarization. The distortion depends on the ground homogeneity and the orientation of the antennas relative to the ground structure. The received signals from the reflecting objects may most times only be classified according to their coverage and intensity. This makes the recognition of the objects difficult or impossible. In airborne and spaceborne Remote Sensing the systems are meanwhile mostly equipped with front ends with dual orthogonal polarized antennas for a full polarimetric operation. The received signals, registered in 2x2 scattering matrices according to co- and cross polarization, are processed for the evaluation of all features of the targets. Ground penetrating radars could also profit from the scientific results of Remote Sensing. The classification of detected objects for their structure and orientation requires more information in the reflected signal than can be measured with a single polarization [1, 2]. In this paper dual linear, orthogonal polarized antennas with a common single, frequency independent phase center, are presented [3]. The relative bandwidth of these antennas can be 1:3, up to 1:4. The antenna is designed to work in the frequency range between 3 GHz and 11 GHz, but can be easily adapted to the GPR frequency range by scaling. The size of the antenna scaled for operation in typical GPR frequencies would approximately be 20 by 20 cm2. By the implementation in a dielectric carrier it could be reduced in size if required. The major problem for ultra wide band, dual polarized antennas is the frequency independent feed network, realizing the required phase shifts. For these antennas a network, which is frequency independent over a wide range, has been

  8. Broadband Loaded Cylindrical Monopole Antenna

    OpenAIRE

    Boucher, Solene; Sharaiha, Ala; Potier, Patrick

    2013-01-01

    Ahstract-A broadband printed monopole antenna based on the variation of the conductivity along its length is proposed .. The result indicates that a non-monotonous repartition provides interesting performances in terms of impedance bandwidth but also concerning antenna gain. The achievement of the method is demonstrated through its application, using the carbon fibers to perform this conductivity variation. Monopole antenna presents a large impedance bandwidth of 123% with an interesting gain...

  9. Size, gain and bandwidth trade-offs for wideband diamond dipole with AMC reflector

    Science.gov (United States)

    Joshi, Chetan; Lepage, Anne Claire; Sarrazin, Julien; Begaud, Xavier

    2016-03-01

    Compact and directive ultra-wideband antennas are required in variety of applications. Directional wideband antennas can be designed by using a reflector to redirect the energy back in half space and increase the gain. Use of artificial magnetic conductors (AMC) as reflectors for antennas allows reduction in the thickness of an antenna using traditional perfect electrical conductors (PEC) reflectors. The lateral size of the reflector also has an important effect on the antenna performance. In this paper, we study the trade-offs involved in the design of an AMC used as a reflector for broadband diamond dipole antenna by simulating various sizes of the reflector.

  10. Design and Analysis of Printed Yagi-Uda Antenna and Two-Element Array for WLAN Applications

    OpenAIRE

    Cai Run-Nan; Yang Ming-Chuan; Lin Shu; Zhang Xing-Qi; Zhang Xin-Yue; Liu Xiao-Feng

    2012-01-01

    A printed director antenna with compact structure is proposed. The antenna is fed by a balanced microstrip-slotline and makes good use of space to reduce feeding network area and the size of antenna. According to the simulation results of CST MICROWAVE STUDIO software, broadband characteristics and directional radiation properties of the antenna are explained. The operating bandwidth is 1.8 GHz–3.5 GHz with reflection coefficient less than −10 dB. Antenna gain in band can achieve 4.5–6.8 dBi,...

  11. UWB Directive Triangular Patch Antenna

    Directory of Open Access Journals (Sweden)

    A. C. Lepage

    2008-01-01

    Full Text Available Compact directive UWB antennas are presented in this paper. We propose an optimization of the F-probe fed triangular patch antenna. The new design achieves an impedance bandwidth of 69% (3–6.15 GHz and presents good radiation characteristics over the whole impedance bandwidth. The average gain is 6.1 dB. A time-domain study has been performed to characterize the antenna behavior in case a UWB pulse is used. Finally, we propose an alternative solution to facilitate the manufacturing process using metallized foam technology. It also improves the robustness of the antenna as well as reducing its cost.

  12. Antenna arrays a computational approach

    CERN Document Server

    Haupt, Randy L

    2010-01-01

    This book covers a wide range of antenna array topics that are becoming increasingly important in wireless applications, particularly in design and computer modeling. Signal processing and numerical modeling algorithms are explored, and MATLAB computer codes are provided for many of the design examples. Pictures of antenna arrays and components provided by industry and government sources are presented with explanations of how they work. Antenna Arrays is a valuable reference for practicing engineers and scientists in wireless communications, radar, and remote sensing, and an excellent textbook for advanced antenna courses.

  13. Hybrid Maritime Satellite Communication Antenna

    DEFF Research Database (Denmark)

    Smith, Thomas Gunst

    Hybrid antennas for a maritime satellite communication terminal with simultaneous operation at L- and Ka-band have been investigated. The frequency bands of interest are 1; 525:0 1; 660:5 MHz (RX+TX, RHCP), 19:7 20:2 (RX, LHCP) and 29:5 30:0 GHz (TX, RHCP), which are all part of the Inmarsat BGAN...... and Inmarsat GX services, respectively. The results of this study are three antenna concepts, which demonstrates high performance at both L- and Ka-band. A combined single/dual-reflector antenna is designed, which presents a favourable way of combining feed antennas for the diverse frequencies. This...... antenna enables the use of a conventional horn-fed dual-reflector for Ka-band, while a backfire helical antenna is used to form a single-reflector antenna at L-band. Simulations show excellent performance of the L-band backfire helical reflector antenna, due to the utilization of the entire antenna...

  14. Minimum Q Electrically Small Antennas

    DEFF Research Database (Denmark)

    Kim, O. S.

    2012-01-01

    Theoretically, the minimum radiation quality factor Q of an isolated resonance can be achieved in a spherical electrically small antenna by combining TM1m and TE1m spherical modes, provided that the stored energy in the antenna spherical volume is totally suppressed. Using closed-form expressions...... results for a multiarm spherical helix antenna confirm the theoretical predictions. For example, a 4-arm spherical helix antenna with a magnetic-coated perfectly electrically conducting core (ka=0.254) exhibits the Q of 0.66 times the Chu lower bound, or 1.25 times the minimum Q....

  15. Coupling element antenna with slot tuning for handheld devices at LTE frequencies

    DEFF Research Database (Denmark)

    Barrio, Samantha Caporal Del; Pelosi, Mauro; Franek, Ondrej; Pedersen, Gert Frølund

    2012-01-01

    Tunable antennas are a promising way to overcome bandwidth limitations for the new communication standards. Since it is the chassis that resonates in the low frequencies, its tuning is pertinent and allows for more compact size designs. This paper proposes a coupling element based antenna. A reco...

  16. Microstrip Folded Dipole Antenna for 35 GHz MMW Communication

    OpenAIRE

    Guang Hua; Chen Yang; Ping Lu; Hou-Xing Zhou; Wei Hong

    2013-01-01

    A microstrip asymmetric folded dipole antenna on chip is proposed in this paper. The construction of balun feed line is adopted to provide wideband. A new design procedure based on the odd-even mode method to calculate the input impedance of an asymmetric strip folded dipole antenna is presented. The folded dipole antenna has the advantage of small size, low profile, low cost, and so forth. The measured results show that a miniaturized antenna has the bandwidth of more than 14.2% (VSWR ≤ 2); ...

  17. Feeding position Effects on the performance of Planar Inverted Folded Antenna

    Directory of Open Access Journals (Sweden)

    B.T.P.Madhav

    2011-10-01

    Full Text Available PIFA’s are used in many applications like PCS, mobile handsets, Bluetooth, WLAN, WI-FI etc. The position of the feed and the patch dimension will play a major role in the performance of the antenna along with substrate, material. The method of improving the bandwidth and reduction of size of the antenna can be alone carried by selecting these PIFA antennas. The design and characterization of the PIFA with respect to the feeding position is to be analyzed in this present work. Different feeding positions are considered and verified the output parameters of the antenna and analyzed the results.

  18. 3D printed 20/30-GHz dual-band offset stepped-reflector antenna

    DEFF Research Database (Denmark)

    Menendez, Laura G.; Kim, Oleksiy S.; Persson, Frank;

    2015-01-01

    peak directivity of 36.7 dB and 40.4 dB at 20 and 30 GHz, respectively; this corresponds to an aperture efficiency of 61 % and 64 %, respectively. These results demonstrate that 3D printing is a viable manufacturing technology for medium-sized high-frequency antennas.......This paper documents the manufacturing by selective laser sintering of a 20/30 GHz dual-band circularly polarized offset stepped-reflector antenna for K- and Ka-band satellite communication. The manufactured antenna has been measured at the DTU-ESA Spherical Near-Field Antenna Test Facility with a...

  19. Omnidirectional Antenna with Multi-Resonance Performance for Microwave Imaging Systems

    Directory of Open Access Journals (Sweden)

    N. Ojaroudi

    2013-11-01

    Full Text Available In this paper, a novel ultra-wideband printed monopole antenna (PMA for microwave imaging systems is presented. The proposed antenna provides a wide usable fractional bandwidth of more than 160% (2.12-17.87 GHz. The antenna has an ordinary square radiating patch, therefore displays a good omni-directional radiation pattern even at higher frequencies and also its radiation efficiency is greater than 82% across the entire radiating band. The designed antenna has a small size of 12×18 mm2.

  20. Omnidirectional Antenna with Multi-Resonance Performance for Microwave Imaging Systems

    OpenAIRE

    N. Ojaroudi; M. Ojaroudi; F. Geran; Amiri , S . (MSc)

    2013-01-01

    In this paper, a novel ultra-wideband printed monopole antenna (PMA) for microwave imaging systems is presented. The proposed antenna provides a wide usable fractional bandwidth of more than 160% (2.12-17.87 GHz). The antenna has an ordinary square radiating patch, therefore displays a good omni-directional radiation pattern even at higher frequencies and also its radiation efficiency is greater than 82% across the entire radiating band. The designed antenna has a small size of 12×18 mm2.

  1. Low-Cost Dielectric Substrate for Designing Low Profile Multiband Monopole Microstrip Antenna

    OpenAIRE

    M. R. Ahsan; Islam, M. T.; M. Habib Ullah; Arshad, H; M. F. Mansor

    2014-01-01

    This paper proposes a small sized, low-cost multiband monopole antenna which can cover the WiMAX bands and C-band. The proposed antenna of 20 × 20 mm2 radiating patch is printed on cost effective 1.6 mm thick fiberglass polymer resin dielectric material substrate and fed by 4 mm long microstrip line. The finite element method based, full wave electromagnetic simulator HFSS is efficiently utilized for designing and analyzing the proposed antenna and the antenna parameters are measured in a sta...

  2. Monopole Crescent Elliptical Antenna with Band-Notched Characteristics for UWB Applications

    Institute of Scientific and Technical Information of China (English)

    JIAO Shengcai; GE Ning; LU Jianhua; JIANG Ming

    2009-01-01

    A compact antenna with extended band-notched characteristics was designed for ultra wideband (UWB) communications. The antenna consists of a crescent-shaped elliptical patch with a T-shaped stub and a square ground board plane. The antenna is easily integrated with radio-frequency/microwave circuits to reduce the manufacturing cost. The central frequency and the notch bandwidth can be adjusted by changing the size of the T-shaped stub. Simulations verify the design characteristics. Measurements show that the antenna produces the UWB working bandwidth.

  3. Modified antenna for orthogonally polarised fields

    OpenAIRE

    Prudyus, Ivan N.; Zakharia, Y. A.; Storozh, V. G.; Mankovsky, S. V.

    2005-01-01

    A compact wideband antenna for transmission and receiving of orthogonally polarized electromagnetic fields is proposed. Results of electrodynamic antenna structure analysis are considered. Main antenna properties by results of experimental investigation are presented.

  4. Ultrawideband method of feeding a dipole antenna

    OpenAIRE

    Bakhrakh, Lev D.; Los', V. F.; Shamanov, A. N.

    2003-01-01

    An antenna-feeder device is considered, in which a new way of antenna excitation is implemented. An example is presented of its use with a dipole antenna for the radiation of super-short pulse signals.

  5. Antenna system for measuring electromagnetic field parameters

    OpenAIRE

    Ilnitskiy, Ludvig Ya.; Shcherbyna, Olga A.

    2014-01-01

    A functional block diagram of the general-purpose antenna system for measuring electromagnetic wave parameters has been presented. Theoretical relationships forming a basis of the antenna system structure are described, and the antenna operation principle is presented.

  6. Ferrite attenuator modulation improves antenna performance

    Science.gov (United States)

    Hooks, J. C.; Larson, S. G.; Shorkley, F. H.; Williams, B. T.

    1970-01-01

    Ferrite attenuator inserted into appropriate waveguide reduces the gain of the antenna element which is causing interference. Modulating the ferrite attenuator to change the antenna gain at the receive frequency permits ground tracking until the antenna is no longer needed.

  7. Salt stress change chlorophyll fluorescence in mango

    Directory of Open Access Journals (Sweden)

    Cicero Cartaxo de Lucena

    2012-12-01

    Full Text Available This study evaluated the tolerance of mango cultivars 'Haden', 'Palmer', 'Tommy Atkins' and 'Uba' grafted on rootstock 'Imbú' to salt stress using chlorophyll fluorescence. Plants were grown in modified Hoagland solution containing 0, 15, 30, and 45 mmol L-1 NaCl. At 97 days the parameters of the chlorophyll fluorescence (F0, Fm, Fv, F0/Fm, Fv/Fm, Fv'/Fm', ΦPSII = [(Fm'-Fs/(Fm'], D = (1- Fv'/Fm' and ETR = (ΦPSII×PPF×0,84×0,5 were determined. At 100 days, the leaf emission and leaf area, toxicity and leaf abscission indexes were determined. In all cultivars evaluated, in different degree, there were decreases in photochemical efficiency of photosystem II, enhanced concentrations from 15 mmol L-1 NaCl. The decreases in the potential quantum yield of photosystem II (Fv/Fm were 27.9, 18.7, 20.5, and 27.4%, for cultivars 'Haden', 'Palmer', 'Tommy Atkins', and 'Uba', respectively, when grown in 45 mmol L-1 NaCl. It was found decreases in leaf emission and mean leaf area in all cultivars from 15 mmol L-1 NaCl. There were increases in leaf toxicity of 33.0, 67.5, 41.6 and 80.8% and in leaf abscission of 71.8, 29.2, 32.5, and 67.9% for the cultivars 'Haden', 'Palmer', 'Tommy Atkins', and 'Uba' respectively, when grown in 45 mmol L-1 NaCl. Leaf toxicity and leaf abscission were not observed in 15 mmol L-1 NaCl. The decrease in Fv/Fm ratio were accompanied by decreasing in leaf emission and increased leaf toxicity index, showing, therefore, the potential of chlorophyll fluorescence in the early detection of salt stress in mango tree.

  8. The Magnesium Chelation Step in Chlorophyll Biosynthesis

    Energy Technology Data Exchange (ETDEWEB)

    Gregory L. Dilworth, Ph.D Chemical Sciences, Geosciences and Biosciences Division Office of Basis Energy Sciences, greg.dilworth@science.doe.gov

    2001-01-17

    The progress described in this report encompasses work supported by DOE grant DE-FG09-89ER13989 for the period 2/15/92 to the present 6/14/94. The goals of the project were to continue investigating the enzymology of Mg-chelatase and to investigate the co-regulation of heme and chlorophyll formation in intact plastids. During this period the laboratory had additional support (two years) from USDA to investigate heme metabolism in chloroplasts. This report is arranged so that the progress is described by reference to manuscripts which are published, under review or in preparation.

  9. Photo-bleaching response in chlorophyll solutions

    International Nuclear Information System (INIS)

    Photo-excitation processes were investigated in chlorophyll solutions by irradiation with UV light sources. Photo-excited bulk effects during the bleaching experiments were diagnosed. The optical diagnostic was expressed by a Beer-Lambert matrix formulation and applied to the experimental results. The chromophores evaluated optical cross-section was 10-15 cm2 and the optical absorption coefficient dynamic variation was fitted to a simple reaction rate model. The bleaching rates were expressed by this model and fitted to the experimental data

  10. Effect of discharge on the chlorophyll a distribution in the tidally-influenced Potomac River

    Science.gov (United States)

    Bennett, J.P.; Woodward, J.W.; Shultz, D.J.

    1986-01-01

    In the tidal Potomac River, high river discharges during the spring are associated with high chlorophyll a concentrations in the following in the following summer, assuming that summertime light and temperature conditions are favorable. Spring floods deliver large loads of particulate N and P to the tidal river. This particulate N and P could be mineralized by bacteria to inorganic N and P and released to the water column where it is available for phytoplankton use during summertime. However, during the study period relatively low concentrations of chlorophyll a (less than 50 ??g l-1 occurred in the tidal river if average monthly discharge during July or August exceeded 200 m3s-1. Discharge and other conditions combined to produce conditions favorable for nuisance levels of chlorophyll a (greater than 100 ??g l-1 approximately one year out of four. Chlorophyll a maxima occurred in the Potomac River transition zone and estuary during late winter (dinoflagellates) and spring (diatoms). Typical seasonal peak concentrations were achieved at discharges as high as 970 m3 s-1, but sustained discharges greater than 1,100 m3 s-1 retarded development. Optimum growth conditions occurred following runoff events of 10 to 15 d duration which produced transit times to the transition zone of 7 to 10 d. Wet years with numerous moderate-sized runoff events, such as 1980, tend to produce greater biomass in the transition zone and estuary than do dry years such as 1981. ?? 1986 Estuarine Research Federation.

  11. Design aspects of commercial satellite antennas

    Science.gov (United States)

    Lang, K. C.; Taormina, F. A.

    General design considerations for commercial satellite antennas are reviewed, and design factors of shaped beam reflector antennas are described, including shaped beam efficiency, flat-topping and boundary matching, and analysis by Fourier transforms. Attention is then given to the design of the Telesat Anik 17/Westar/Palapa communications antenna, the Comstar I communications antenna, the SBS communications antenna, and Intelsat IV A communications antenna.

  12. Ultra wideband antennas design, methodologies, and performance

    CERN Document Server

    Galvan-Tejada, Giselle M; Jardón Aguilar, Hildeberto

    2015-01-01

    Ultra Wideband Antennas: Design, Methodologies, and Performance presents the current state of the art of ultra wideband (UWB) antennas, from theory specific for these radiators to guidelines for the design of omnidirectional and directional UWB antennas. Offering a comprehensive overview of the latest UWB antenna research and development, this book:Discusses the developed theory for UWB antennas in frequency and time domainsDelivers a brief exposition of numerical methods for electromagnetics oriented to antennasDescribes solid-planar equivalen

  13. Broadband Corrugated Square-Shaped Monopole Antenna

    OpenAIRE

    S. D. Ahirwar; C. Sairam

    2011-01-01

    Design and development of a corrugated square-shaped monopole antenna is presented with measured results. The operational bandwidth of the antenna is 300 MHz–3000 MHz. The antenna is derived from a square-shaped planar monopole antenna. This basic square-shaped radiating element is corrugated in its lateral dimension. This corrugation reduces the lateral dimension of the antenna by 60%. Electrical performance of this antenna is better than its parent counterpart. This paper presents design an...

  14. UWB and SWB Planar Antenna Technology

    OpenAIRE

    Zhong, Shun-Shi

    2010-01-01

    The recent progress in the development of UWB planar antenna technology has been reviewed. Some types of UWB metal-plate monopole antennas, UWB printed monopole antennas and UWB printed slot antennas are presented. The comparison results of indicate that the UWB printed monopole antennas can realize relatively smaller dimensions, and that the UWB printed slot antennas can achieve relatively higher gain. Finally, some realization manners of the band-notch function of UWB printed monopole anten...

  15. PARAMETRIC ANALYSIS OF A MINIATURIZED INVERTED II SHAPED ANTENNA FOR WIRELESS SENSOR NETWORK APPLICATIONS

    Directory of Open Access Journals (Sweden)

    M. Shanmugapriya

    2015-06-01

    Full Text Available A compact and simple design of a CPW-fed planar antenna for wireless sensor network antenna application with a better size reduction is presented. The proposed antenna consists of an inverted ? shaped metal patch on a printed circuit board fed by a 50-O coplanar waveguide (CPW. The parametric analysis of length and width are made. The designed antenna’s physical dimensions are 32 mm (length x 26 mm (width x 1.6 mm (height. The antenna structure has been modeled and fabricated and its performance has been evaluated using a method of moment based electromagnetic simulator, IE3D .The return loss of -22.5 dB and VSWR of 1.34 dB are noted. The radiation pattern of the antenna proves that it radiates in all direction. The antenna is fabricated and tested and the measured results go in good agreement with simulated one.

  16. A Study on a Miniaturized Planar Spiral Antenna for Partial Discharge Detection in GIS

    Directory of Open Access Journals (Sweden)

    Wang Yongqiang

    2015-01-01

    Full Text Available Ultra-high frequency (UHF detection method can effectively detect the signals of partial discharge (PD in electrical equipment. Hence the authors designed a sensor of miniaturized planar spiral antenna for detecting PD in gas insulated substations (GISs, which is sine-wave meandered based on the traditional Archimedean spiral antenna in order to reduce the antenna’s size. The test results indicate that this antenna has a wide-frequency band of 0.92~3GHz in terms of the voltage standing wave ratio (VSWR which is smaller than 2. The antenna is smaller and its structure is simpler, its diameter is 97mm and its height is 51mm; Besides, this antenna has an ultra-wideband, great directivity and the feature of omnidirectional radiation. Therefore, the proposed antenna is quite promising for PD on-line detection applications.

  17. Broad-band Circularly Polarized Patch Antenna for Multi-Mode Navigation Application

    Directory of Open Access Journals (Sweden)

    Wangencheng

    2012-11-01

    Full Text Available A broad-band circularly polarizedpatch antenna is developed for GPS/ GLONASS/ BEIDOU/ GALILEO systems. The antenna includes four L-probes, a circular patch with four edges trimming and a feed network. The four L-probes are excited by a feed network in equal magnitude and successive 90 phase difference. The edge cutting method is used to improve the axial ratio, impedance bandwidth and reduced the size of the antenna. The measured gains at 1227 and 1575 MHz are about 8 and 10 dB respectively. The 10 dB return loss bandwidth of the antenna is 42.9% from 1.1 to 1.7 GHz; the 3 dB axial ratio bandwidth of the antenna is 30% from 1.19 to 1.61 GHz. Low multipath effects have been observed of the antenna.

  18. Yagi-Uda optical antenna array collimated laser based on surface plasmons

    Science.gov (United States)

    Ma, Long; Lin, Jie; Ma, Yuan; Liu, Bin; Tan, Jiubin; Jin, Peng

    2016-06-01

    The divergence and directivity of a laser with a periodic Yagi-Uda optical antenna array modulated surface are investigated by finite element method. The nanoparticle optical antenna arrays are optimized to achieve the high directivity and the small divergence by using of Helmholtz's reciprocity theorem. When the nanoparticle antenna replaced by a Yagi-Uda antenna with same size, the directivity and the signal-to-noise ratio of the modulated laser beam are notably enhanced. The main reason is that the directors of the Yagi-Uda antennas induce more energy to propagate towards the antenna transmitting direction. The results can provide valuable guidelines in designing collimated laser, which can be widely applied in the field of biologic detection, spatial optical communication and optical measurement.

  19. Design of a broadband hexagonal-shaped zeroth-order resonance antenna with metamaterials

    Energy Technology Data Exchange (ETDEWEB)

    Woo, Dong Sik; Kim, Kang Wook; Choi, Hyun Chul [Kyungpook National University, Daegu (Korea, Republic of)

    2014-11-15

    A broadband hexagonal-shaped metamaterials (MTMs)-based zeroth-order resonant (ZOR) antenna was designed and fabricated. The hexagonal shape of a top patch on a mushroom structure makes not only direct-current paths between the two ends of the patch but also round-current paths along the outside of the patch, thereby widening the resonance frequency of the mushroom MTM antenna. According to the shape of the hexagon patch, the presented antenna achieved impedance bandwidth of 58.6% corresponding to ultra-wideband technology. The proposed ZOR antenna was modeled by utilizing a composite right- and left-handed (CRLH) transmission line and provided 4 to 9.3 dBi of the antenna gain with reduced size as compared to conventional microstrip antennas at Ku- to K-band frequencies.

  20. Multiband Cross Dipole Antenna Based On the Triangular and Quadratic Fractal Koch Curve

    Directory of Open Access Journals (Sweden)

    Fawwaz Jinan Jibrael

    2010-08-01

    Full Text Available This paper present the analysis and design a small size, low profile andmultiband fractal cross dipole antenna. The proposed antenna design,analysis and characterization had been performed using the method ofmoments (MoM technique. The new designed antenna has operatingfrequencies of 0.543 GHz, 2 GHz, and 6.5 GHz with acceptable bandwidthwhich has useful applications in communication systems. The radiationcharacteristics and reflection coefficient of the proposed antenna weredescribed and simulated using 4NEC2 software package. Also, the gain ofthis proposed antenna is calculated and described in the three planes are XZplane,YZ-plane, and XY-plane, where the antenna placed in the free space.

  1. Isolation of chlorophylls from stinging nettle (Urtica dioica L.)

    OpenAIRE

    Hojnik, Maša; Škerget, Mojca; Knez, Željko

    2012-01-01

    This study was aimed to assess the feasibility of extracting chlorophylls fromstinging nettle (Urtica dioica L.) by solvent extraction. In preliminary, the investigation concerned three parts of raw material (leaves, stalk and whole plant), different preservation techniques (blanching and drying) and different storage temperatures of preserved material ( |20 C for blanched and 4 C for dried sample). Extracts were analysed for chlorophyll A and chlorophyll B, respectively, by means of HPLC met...

  2. In vitro complexes of copper and zinc with chlorophyll

    OpenAIRE

    JELENA PETROVIC; GORAN NIKOLIC; DEJAN MARKOVIC

    2006-01-01

    Complexes of copper and zinc with chlorophyll, the major photosynthesis pigment, were studied by Vis, FTIR and fluorescence spectroscopy. Two types of complexes were recognized. While copper replaces the central magnesium atom of chlorophyll to form a “central” Cu–Chl complex, this was not proposed in the case of zinc. Instead, the zinc-mediated formation of a 6-membered chelate cycle fused at the periphery of the chlorophyll structure is proposed. The latter event could be ascribed to allome...

  3. Surface disturbance of cryptobiotic soil crusts: nitrogenase activity, chlorophyll content, and chlorophyll degradation

    Science.gov (United States)

    Belnap, Jayne; Harper, Kimball T.; Warren, Steven D.

    1994-01-01

    Cryptobiotic soil crusts are an important component of semiarid and arid ecosystems. An important role of these crusts is the contribution of fixed nitrogen to cold‐desert ecosystems. This study examines the residual effects of various intensities and combinations of different surface disturbances (raking, scalping, and tracked vehicles) on nitrogenase activity, chlorophyll content, and chlorophyll degradation in these soil crusts. Nine months after disturbance chlorophyll content of disturbed soils was not statistically different from undisturbed controls, except in the scalped treatments, indicating recovery of this characteristic is fairly quick unless surface material is removed. Differences in chlorophyll degradation among treatments were not statistically significant. However, nitrogenase activity in all treatments showed tremendous reductions, ranging from 77–97%, when compared to the control, indicating this characteristic is slow to recover. Consequently, assessment of crustal recovery from disturbance must include not only visual and biomass characteristics but other physiological measurements as well. Areas dominated by these crusts should be managed conservatively until the implications of crustal disturbance is better understood.

  4. Computer Reconstruction of Plant Growth and Chlorophyll Fluorescence Emission in Three Spatial Dimensions

    OpenAIRE

    Ladislav Nedbal; David Šebela; Chandra Bellasio; Radek Tesař; Julie Olejníčková

    2012-01-01

    Plant leaves grow and change their orientation as well their emission of chlorophyll fluorescence in time. All these dynamic plant properties can be semi-automatically monitored by a 3D imaging system that generates plant models by the method of coded light illumination, fluorescence imaging and computer 3D reconstruction. Here, we describe the essentials of the method, as well as the system hardware. We show that the technique can reconstruct, with a high fidelity, the leaf size, the leaf an...

  5. Antennas - Our electronic eyes and ears

    Science.gov (United States)

    Kraus, John D.

    1989-01-01

    Although the number of antenna types is vast, all antenna properties may be characterized in terms of the same basic parameters of radiation pattern, impedance, radar cross-section, and temperature. A comprehensive introduction is presented to antenna configurations; these encompass, among antennas constructed of wire or tubing, such wideband and circularly polarized types as helices, linear conductors, and loops. Sheet-conductor antenna families include reflectors, waveguides, and slotted antennas. Nonconducting dielectric antennas are lenses, polyrods, and slabs. Antenna array types range over 'driven', parasitic, and adaptive configurations. 'Two half-wavelength' and 'four half-wavelength' element arrays are also discussed.

  6. Design of Antennas for RFID Application

    OpenAIRE

    Zhang, Ming-Tao; Jiao, Yong-Chang; Zhang, Fu-Shun; Wang, Wu-Tu

    2009-01-01

    In this chapter, the antenna in RFID system is discussed, and the design of antenna is also described. The main contents include the status of the antenna in the RFID system, the design method for the antenna, the power transmission between the tag chip and the tag antenna, the tag antenna design, the scheme and design for the circular polarization, and the design of antenna for microwave band RFID tag. These researches almost cover all problems of the antenna encountering in the RFID applica...

  7. Wideband E-Shaped Microstrip Antenna for Wireless Sensor Networks

    Directory of Open Access Journals (Sweden)

    G. Elangovan

    2012-01-01

    Full Text Available Problem statement: Wireless Sensor Networks (WSN is currently receiving significant attention due to their unlimited potential. However, it is still very early in the lifetime of such systems and many research challenges exist, out of which one of the challenges is sensor processing and fusion under limited capacities, the most important component in sensor is its TX/RX antenna. Approach: For high-speed wireless local area networks and other wireless communication systems covering the 5.33-5.71 GHz frequency band. In this frequency band microstrip antennas have attracted with its low-profile in nature. In this study, microstrip antenna is proposed to meet the challenges, which combines the advantages of compactness with the low cost and low profile of a patch antenna. Results: The key parameters governing the antenna optimization have been determined with the help of High Frequency Simulation Software (HFSS. As a consequence, 5.5GHz microstrip antenna with size 22×16×3.2 mm has been realized on duroid with 2.2. Conclusion: This combination of performance metrics is highly desirable for autonomous distributed sensor network applications where a small sensor node volume and excellent power efficiency are required.

  8. Remote sensing of terrestrial chlorophyll fluorescence from space

    OpenAIRE

    Frankenberg, Christian; Berry, Joseph; Guanter, Luis; JOINER Joanna

    2013-01-01

    High-resolution spectrometers enable new avenues in global carbon cycle research, including the first accurate retrievals of chlorophyll fluorescence from space as an indicator of photosynthetic activity.

  9. [Estimation of canopy chlorophyll content using hyperspectral data].

    Science.gov (United States)

    Dong, Jing-Jing; Wang, Li; Niu, Zheng

    2009-11-01

    Many researches have developed models to estimate chlorophyl content at leaf and canopy level, but they were species-specific. The objective of the present paper was to develop a new model. First, canopy reflectance was simulated for different species and different canopy architecture using radiative transfer models. Based on the simulated canopy reflectance, the relationship between canopy reflectance and canopy chlorophyll content was studied, and then a chlorophyll estimation model was built using the method of spectral index. The coefficient of determination (R2) between spectral index based model and canopy chlorophyll content reached 0.75 for simulated data. To investigate the applicability of this chlorophyll model, the authors chose a field sample area in Gansu Province to carry out the measurement of leaf chlorophyll content, canopy reflectance and other parameters. Besides, the authors also ordered the synchronous Hyperion data, a hyperspectral image with a spatial resolution of 30 m. Canopy reflectance from field measurment and reflectance from Hyperion image were respectively used as the input parameter for the chlorophyll estimation model. Both of them got good results, which indicated that the model could be used for accurate canopy chlorophyll estimation using canopy reflectance. However, while using spaceborne hyperspectral data to estimate canopy chlorophyll content, good atmospheric correction is required. PMID:20101973

  10. Patch antenna terahertz photodetectors

    International Nuclear Information System (INIS)

    We report on the implementation of 5 THz quantum well photodetector exploiting a patch antenna cavity array. The benefit of our plasmonic architecture on the detector performance is assessed by comparing it with detectors made using the same quantum well absorbing region, but processed into a standard 45° polished facet mesa. Our results demonstrate a clear improvement in responsivity, polarization insensitivity, and background limited performance. Peak detectivities in excess of 5 × 1012 cmHz1/2/W have been obtained, a value comparable with that of the best cryogenic cooled bolometers

  11. Ultra wide band antennas

    CERN Document Server

    Begaud, Xavier

    2013-01-01

    Ultra Wide Band Technology (UWB) has reached a level of maturity that allows us to offer wireless links with either high or low data rates. These wireless links are frequently associated with a location capability for which ultimate accuracy varies with the inverse of the frequency bandwidth. Using time or frequency domain waveforms, they are currently the subject of international standards facilitating their commercial implementation. Drawing up a complete state of the art, Ultra Wide Band Antennas is aimed at students, engineers and researchers and presents a summary of internationally recog

  12. Terahertz antenna electronic chopper

    Energy Technology Data Exchange (ETDEWEB)

    Sterczewski, L. A., E-mail: lukasz.sterczewski@pwr.edu.pl; Grzelczak, M. P.; Plinski, E. F. [Department of Electronics, Wroclaw University of Technology, 27 Wybrzeze Wyspianskiego St., 50-370 Wroclaw (Poland)

    2016-01-15

    In this paper, we present an electronic circuit used to bias a photoconductive antenna that generates terahertz radiation. The working principles and the design process for the device are discussed in detail. The noise and shape of the wave measurements for a built device are considered. Furthermore, their impact on a terahertz pulse and its spectra is also examined. The proposed implementation is simple to build, robust and offers a real improvement over THz instrumentation due to the frequency tuning. Additionally, it provides for galvanic isolation and ESD protection.

  13. Conceptual design of PAM antenna for Aditya-U Tokamak

    International Nuclear Information System (INIS)

    ADITYA Tokamak is being upgraded (ADITYA-U) to operate the machine at enhanced plasma parameter. This also provides an opportunity to upgrade lower hybrid current drive (LHCD) system to drive plasma current non-inductively and enhance the coupling of RF power to the plasma. It is proposed to replace existing grill antenna by a new type of antenna which is often referred as passive active multijunction (PAM) antenna. The PAM antenna has an advantage of providing efficient RF coupling to the plasma, even at edge densities close to cut-off. Further it provides a lower reflection from the plasma as compared to the conventional grill antenna. ADITYA-U would operate at toroidal magnetic field of 1.5T and may have line average density lying in the range of (0.8 - 3.0) X 1019 m-3. For LHW's to access to the plasma center, the waves would be launched having parallel refractive index (N∥) which is well above the critical accessible condition given by Stix. Thus the PAM antenna is designed to launch N∥ of 2.25 ± 0.28. Our analysis reveals that periodicity for the PAM antenna would be 27mm to launch the design value of N∥ with three passive and three active waveguide in a single PAM module having phase shift of 270° between adjacent active waveguides. The size of the radial port (490 mm x 190 mm) of ADITYA-U tokamak determines the number of PAM modules which may be accommodated in the new scheme. It turns out that two modules of PAM antenna may be accommodated in the said radial port. Mode convertors (TE10 to TE30 mode) would be employed for dividing the RF power in three poloidal locations. A thermal and electro-mechanical analysis is also discussed in this paper. (author)

  14. The magnesium chelation step in chlorophyll biosynthesis

    Energy Technology Data Exchange (ETDEWEB)

    Weinstein, J.D.

    1991-01-01

    The biogenesis of energy transducing membranes requires the coordinate synthesis of prosthetic groups, proteins and lipids. Two of the major prosthetic groups, chlorophyll and heme, share a common biosynthetic pathway that diverges at the point of metal insertion into protoporphyrin IX. Insertion of iron leads to heme, while insertion of magnesium leads to chlorophyll. The Mg-chelatase from intact cucumber chloroplasts has been characterized with regard to substrate specificity, regulation, ATP requirement, and a requirement for intact chloroplasts. Mg-chelatase was isolated from maize, barley and peas and characterized in order to circumvent the intact chloroplast requirement of cucumber Mg-chelatase. Pea Mg-chelatase activity is higher than cucumber Mg-chelatase activity, and lacks the requirement for intact chloroplasts. Studies on isolated pea Mg-chelatase have shown more cofactors are required for the reaction than are seen with ferrochelatase, indicating a greater opportunity for regulatory control of this pathway. Two of the cofactors are proteins, and there appears to be a requirement for a protease-sensitive component which is outside the outer envelope. We are developing a continuous spectrophotometric assay for Mg-chelatase activity, and an assay for free heme which has shown heme efflux from intact chloroplasts. 18 refs. (MHB)

  15. Broadband antenna with frequency scanning

    Directory of Open Access Journals (Sweden)

    A. A. Shekaturin

    2014-06-01

    Full Text Available Relevance of this study. The main advantage of frequency scanning is simplicity of implementation. At this point, multifunctional usage of microwave modules is an urgent task, as well as their maximum simpler and cheaper. Antenna design and operation. The study is aimed at providing electric antenna with frequency scanning. It was based on the log-periodic antenna due to its wideband and negotiation capability over the entire operating frequency range. For this distribution line is bent in an arc of a circle in a plane blade while vibrators are arranged along the radius. Computer modeling of antennas with frequency scanning. Modeled with a non-mechanical motion antenna beam emitters representing system for receiving a radio frequency signal on mobile objects calculated for 1.8 GHz ... 4.2 GHz. The simulation was performed in a software environment for numerical modeling of electromagnetic «Feko 5.5». Analysis of the interaction of radiation is based on the method of moments. Findings. The result of this work is to propose a new design of the antenna with a frequency scanning method as agreed in a wide frequency range. In the studied technical solution provided by the rotation of NAM in the frequency range, and the matching of the antenna to the feed line is maintained. Application of this type of antennas on the proposed technical solution in communication systems will improve the communication reliability by maintaining coordination in the frequency range

  16. Slot-Coupled Barbel Antenna

    DEFF Research Database (Denmark)

    Jørgensen, Kasper Lüthje; Jakobsen, Kaj Bjarne

    2016-01-01

    A novel slot-coupled barbel antenna is designed and analyzed. A sensitivity analysis performed in order to improve the bandwidth, while the center frequency is kept constant.......A novel slot-coupled barbel antenna is designed and analyzed. A sensitivity analysis performed in order to improve the bandwidth, while the center frequency is kept constant....

  17. Coupling between minimum scattering antennas

    DEFF Research Database (Denmark)

    Andersen, J.; Lessow, H; Schjær-Jacobsen, Hans

    1974-01-01

    Coupling between minimum scattering antennas (MSA's) is investigated by the coupling theory developed by Wasylkiwskyj and Kahn. Only rotationally symmetric power patterns are considered, and graphs of relative mutual impedance are presented as a function of distance and pattern parameters. Crossed......-dipoles and helices are considered in order to establish a correspondence with simple antenna structures....

  18. Wirelessly powered micro-tracer enabled by miniaturized antenna and microfluidic channel

    Science.gov (United States)

    Duan, G.; Zhao, X.; Seren, H. R.; Chen, C.; Zhang, X.

    2015-12-01

    A miniaturized antenna, 380μm by 380μm in size, was fabricated and integrated with a commercialized passive RFID chip to form a micro-tracer, whose size was 2mm by 1mm in total. The micro-tracer was wirelessly powered and interrogated by a single layer spiral reader antenna through near field coupling. To maximize the working distance, the resonant frequency of micro-tracer and reader antenna were matched at 840MHz. Due to the ultra small size of the tracer antenna, power transfer efficiency decreased dramatically as the distance between tracer antenna and reader antenna increased, thus the working distance of the microtracer was limited within 1mm. To achieve massive operation of the micro-tracer, a microfluidic platform was fabricated with in channel focusing and separation. Acrylic sheets were laser cut to define the channel and cover structure, then bonded together layer by layer with a glass substrate, on which reader antenna was integrated. Pump oil was used as the fluidic media carrying the micro-tracer flowing inside the microfluidic channel. The wireless power transfer and real-time communication was demonstrated with the micro-tracer flowing above the reader antenna, as the ID of the micro-tracer was retrieved and displayed on a computer screen.

  19. Graphene-antenna sandwich photodetector.

    Science.gov (United States)

    Fang, Zheyu; Liu, Zheng; Wang, Yumin; Ajayan, Pulickel M; Nordlander, Peter; Halas, Naomi J

    2012-07-11

    Nanoscale antennas sandwiched between two graphene monolayers yield a photodetector that efficiently converts visible and near-infrared photons into electrons with an 800% enhancement of the photocurrent relative to the antennaless graphene device. The antenna contributes to the photocurrent in two ways: by the transfer of hot electrons generated in the antenna structure upon plasmon decay, as well as by direct plasmon-enhanced excitation of intrinsic graphene electrons due to the antenna near field. This results in a graphene-based photodetector achieving up to 20% internal quantum efficiency in the visible and near-infrared regions of the spectrum. This device can serve as a model for merging the light-harvesting characteristics of optical frequency antennas with the highly attractive transport properties of graphene in new optoelectronic devices. PMID:22703522

  20. DEA deformed stretchable patch antenna

    International Nuclear Information System (INIS)

    A stretchable patch antenna (SPA) whose frequency is tuned by a planar dielectric elastomer actuator (DEA) is presented in this paper. This mechanically reconfigurable antenna system has a configuration resembling a pre-stretched silicone belt. Part of the belt is embedded with a layer of conductive liquid metal to form the patch antenna. Part of the belt is sandwiched between conductive electrodes to form the DEA. Electrical activation of the DEA results in a contraction of the patch antenna, and as a result, in a variation of its resonance frequency. Design and fabrication steps of this system are presented. Measurement results for deformation, resonance frequency variation and efficiency of the patch antenna are also presented. (paper)

  1. Antenna Miniaturization in Complex Electromagnetic Environments

    DEFF Research Database (Denmark)

    Zhang, Jiaying

    - less communication system into the heading-aids, and these are the antenna miniaturization, the measurement techniques for electrically small antennas and the influence of complex environments on the characteristics of electrically small antennas, respectively. Antenna MiniaturizationIn this...... dissertation, we present several novel designs of electrically small loop antennas for the hearing-aid application. First antenna design is a two-dimensional (2-D) planar differential-fed electrically small loop. The working mechanism of this antenna is based on the capacitive loading and the induc- tive...... coupling between two small loops. An analytical model, simulations, fabrications and measurements are presented for this antenna. Second antenna design is a planar two-turn electrically small loop antenna. The work- ing mechanism of this antenna is based on the capacitive loading, and both the capacitive...

  2. Transcatheter Microwave Antenna

    Science.gov (United States)

    Arndt, Dickey G. (Inventor); Carl, James R. (Inventor); Ngo, Phong (Inventor); Raffoul, George W. (Inventor)

    2001-01-01

    A method, simulation, and apparatus are provided that are highly suitable for treatment of benign prostatic hyperplasia (BPH). A catheter is disclosed that includes a small diameter disk loaded monopole antenna surrounded by fusion material having a high heat of fusion and a melting point preferably at or near body temperature. Microwaves from the antenna heat prostatic tissue to promote necrosing of the prostatic tissue that relieves the pressure of the prostatic tissue against the urethra as the body reabsorbs the necrosed or dead tissue. The fusion material keeps the urethra cool by means of the heat of fusion of the fusion material. This prevents damage to the urethra while the prostatic tissue is necrosed. A computer simulation is provided that can be used to predict the resulting temperature profile produced in the prostatic tissue. By changing the various control features of the catheter and method of applying microwave energy a temperature profile can be predicted and produced that is similar to the temperature profile desired for the particular patient.

  3. Lower Bound for the Radiation $Q$ of Electrically Small Magnetic Dipole Antennas With Solid Magnetodielectric Core

    DEFF Research Database (Denmark)

    Kim, Oleksiy S.; Breinbjerg, Olav

    2011-01-01

    A new lower bound for the radiation $Q$ of electrically small spherical magnetic dipole antennas with solid magnetodielectric core is derived in closed form using the exact theory. The new bound approaches the Chu lower bound from above as the antenna electrical size decreases. For $ka, the new b...... bound is lower than the bounds for spherical magnetic as well as electric dipole antennas composed of impressed electric currents in free space.......A new lower bound for the radiation $Q$ of electrically small spherical magnetic dipole antennas with solid magnetodielectric core is derived in closed form using the exact theory. The new bound approaches the Chu lower bound from above as the antenna electrical size decreases. For $ka, the new...

  4. Design of UWB Planar Monopole Antennas with Etched Spiral Slot on the Patch for Multiple Band-Notched Characteristics

    Directory of Open Access Journals (Sweden)

    Swarup Das

    2015-01-01

    Full Text Available Three types of Ultrawideband (UWB antennas with single, double, and triple notched bands are proposed and investigated for UWB communication applications. The proposed antennas consist of CPW fed monopole with spiral slot etched on the patch. In this paper single, double, and also triple band notches with central frequency of 3.57, 5.12, and 8.21 GHz have been generated by varying the length of a single spiral slot. The proposed antenna is low-profile and of compact size. A stable gain is obtained throughout the operation band except the three notched frequencies. The antennas have omnidirectional and stable radiation patterns across all the relevant bands. Moreover, relatively consistent group delays across the UWB frequencies are noticed for the triple notched band antenna. A prototype of the UWB antenna with triple notched bands is fabricated and the measured results of the antenna are compared with the simulated results.

  5. Light-Harvesting Antenna System from the Phototrophic Bacterium Roseiflexus castenholzii

    Energy Technology Data Exchange (ETDEWEB)

    Collins, Aaron M. [Washington Univ., St. Louis, MO (United States); Qian, Pu [Univ. of Sheffield (United Kingdom); Tang, Qun [Univ. of California, Riverside, CA (United States); Bocian, David F [Univ. of California, Riverside, CA (United States); Hunter, C. Neil [Univ. of Sheffield (United Kingdom); Blankenship, Robert E. [Washington Univ., St. Louis, MO (United States)

    2010-08-12

    Photosynthetic organisms have evolved diverse light-harvesting complexes to harness light of various qualities and intensities. Photosynthetic bacteria can have (bacterio)chlorophyll Qy antenna absorption bands ranging from ~650 to ~1100 nm. This broad range of wavelengths has allowed many organisms to thrive in unique light environments. Roseiflexus castenholzii is a niche-adapted, filamentous anoxygenic phototroph (FAP) that lacks chlorosomes, the dominant antenna found in most green bacteria, and here we describe the purification of a full complement of photosynthetic complexes: the light-harvesting (LH) antenna, reaction center (RC), and core complex (RC-LH). By high-performance liquid chromatography separation of bacteriochlorophyll and bacteriopheophytin pigments extracted from the core complex and the RC, the number of subunits that comprise the antenna was determined to be 15 ± 1. Resonance Raman spectroscopy of the carbonyl stretching region displayed modes indicating that 3C-acetyl groups of BChl a are all involved in molecular interactions probably similar to those found in LH1 complexes from purple photosynthetic bacteria. Finally, two-dimensional projections of negatively stained core complexes and the LH antenna revealed a closed, slightly elliptical LH ring with an average diameter of 130 ± 10 Å surrounding a single RC that lacks an H-subunit but is associated with a tetraheme c-type cytochrome.

  6. An Integrated Protein Chemistry Laboratory: Chlorophyll and Chlorophyllase

    Science.gov (United States)

    Arkus, Kiani A. J.; Jez, Joseph M.

    2008-01-01

    Chlorophyll, the most abundant pigment in nature, is degraded during normal plant growth, when leaves change color, and at specific developmental stages. Chlorophyllase catalyzes the first chemical reaction in this process, that is, the hydrolysis of chlorophyll into chlorophyllide. Here, we describe a series of laboratory sessions designed to…

  7. Modulated Chlorophyll "a" Fluorescence: A Tool for Teaching Photosynthesis

    Science.gov (United States)

    Marques da Silva, Jorge; Bernardes da Silva, Anabela; Padua, Mario

    2007-01-01

    "In vivo" chlorophyll "a" fluorescence is a key technique in photosynthesis research. The recent release of a low cost, commercial, modulated fluorometer enables this powerful technology to be used in education. Modulated chlorophyll a fluorescence measurement "in vivo" is here proposed as a tool to demonstrate basic photosynthesis phenomena to…

  8. Investigating the control of chlorophyll degradation by genomic correlation mining

    Science.gov (United States)

    Chlorophyll degradation is an intricate process that is critical in a variety of plant tissues at different times during the plant life cycle. Many of the photoactive chlorophyll degradation intermediates are exceptionally cytotoxic necessitating that the pathway be carefully coordinated and regulat...

  9. A model for chlorophyll fluorescence and photosynthesis at leaf scale

    NARCIS (Netherlands)

    Tol, van der C.; Verhoef, W.; Rosema, A.

    2009-01-01

    This paper presents a leaf biochemical model for steady-state chlorophyll fluorescence and photosynthesis of C3 and C4 vegetation. The model is a tool to study the relationship between passively measured steady-state chlorophyll fluorescence and actual photosynthesis, and its evolution during the da

  10. Chlorophyll in tomato seeds: marker for seed performance?

    NARCIS (Netherlands)

    Suhartanto, M.R.

    2002-01-01

    Using Xe-PAM, laser induced fluorometry and high performance liquid chromatography we found that chlorophyll was present in young tomato (cv. Moneymaker) seeds and was degraded during maturation. Fluorescence microscopy and imaging showed that the majority of chlorophyll is located in the seed coat

  11. Influence of selected abiotic factors on the decomposition of chlorophylls

    Directory of Open Access Journals (Sweden)

    Gra¿yna Kowalewska

    2001-09-01

    Full Text Available The paper presents the results of experiments to determine the influence of selected physico-chemical factors - oxygen, visible light and temperature - on the decomposition of (1 chlorophylls a, b and c, chlorophyll a derivatives and beta-carotene in acetone solution, and (2 chlorophyll a and beta-carotene in axenic cultures of the blue-green algae Anabaena variabilis. The results indicate that both in acetone extracts and in blue-green algae cultures these pigments were most sensitive to light and oxygen; temperatures of up to 25oC had no marked influence on these compounds. Under anoxia in acetone solution, the stability towards light decreased in the order chlorophyll a, chlorophyll b, chlorophylls c. Chlorophyll a, moreover, was less stable than its derivatives - phaeophorbides, phaeophytins, pyrophaeophytins and steryl chlorins - but more stable than beta-carotene, in the last case also in the blue-green algae cultures. Decomposition of all the pigments proceeded mainly via the breakdown of the porphyrin macrocycle, since the decomposition products were not detected in the VIS range. On the basis of these experiments one can state that while light and oxygen may have a decisive direct influence on the distribution of chlorophylls and beta-carotene in sediments, in the natural environment, temperatures of up to 25oC may have very little immediate effect.

  12. Possibilities of Phased Array Antenna (PAA) for Fusion

    International Nuclear Information System (INIS)

    Principles of the design and optimal choice of the PAA scheme for fusion researches are considered on the base of high power microwave antennas. Results of the analysis of the electromagnetic field structure in dependence on PAA sizes and radiator type are given

  13. Photogeneration of charges in microcrystalline chlorophyll a

    International Nuclear Information System (INIS)

    The electric-field and temperature dependence of hole photogeneration in chlorophyll a (Chla) have been analyzed in terms of electric-field assisted thermal dissociation of charge pairs based on Onsager theory. An excellent agreement between the experimental and theoretical values of the slope-to-intercept ratio, S/I, for the plot of photogeneration efficiency vs. electric field at low field strengths provides a proof for the applicability of the Onsager approach to the photogeneration of charges in Chla. A value of 19 nm has been obtained for Coulomb capture radius, rc, from S/I. From the temperature dependence of photogeneration, the initial separation, r0, of photogenerated electron-hole has been evaluated, and has a value of 1.24 nm. This smaller r0 compared to rc leads to a feeble dissociation probability of electron-hole pairs into free carriers, and may, among other factors, explain the low power conversion efficiencies of Chla photovoltaic cells.

  14. Nonspectroscopic imaging for quantitative chlorophyll sensing

    Science.gov (United States)

    Kim, Taehoon; Kim, Jeong-Im; Visbal-Onufrak, Michelle A.; Chapple, Clint; Kim, Young L.

    2016-01-01

    Nondestructive imaging of physiological changes in plants has been intensively used as an invaluable tool for visualizing heterogeneous responses to various types of abiotic and biotic stress. However, conventional approaches often have intrinsic limitations for quantitative analyses, requiring bulky and expensive optical instruments for capturing full spectral information. We report a spectrometerless (or spectrometer-free) reflectance imaging method that allows for nondestructive and quantitative chlorophyll imaging in individual leaves in situ in a handheld device format. The combination of a handheld-type imaging system and a hyperspectral reconstruction algorithm from an RGB camera offers simple instrumentation and operation while avoiding the use of an imaging spectrograph or tunable color filter. This platform could potentially be integrated into a compact, inexpensive, and portable system, while being of great value in high-throughput phenotyping facilities and laboratory settings.

  15. Influence of ambient sulphur dioxide on chlorophyll

    International Nuclear Information System (INIS)

    For the evaluation of the injury due to SO2 from Indraprashtha (IP) Thermal Power Plant, eight species of trees were selected. Experiment was divided in two sections. Section one include transplanted tree saplings of Bauhinia variegata, Delonix regia, Flcus benghalensis, Putranjiwa roxburghii, Morus indica, Polyalthia longifolia, Leucaena leucocephala and Tabernaemontana coronaria. Here one set of plants was transplanted to polluted site of IP and other set was maintained at non polluted site of Jawaharlal Nehru University (Ecological Nursery). Second section of the study have naturally growing trees of the same species in the vicinity of the transplanted plants. Findings of the present study show that tree species were not safe at polluted site. Maximum chlorophyll reduction occurred in Bauhinia variegata, that is 32.05% (transplanted saplings). In naturally growing trees up to 35.70% reduction was seen in B. variegata. (author). 11 refs., 2 tabs

  16. Metamaterial antennas: the most successful metamaterial technology?

    DEFF Research Database (Denmark)

    Breinbjerg, Olav

    2015-01-01

    The Thomson Reuters Web of Science™ lists more than 1500 journal articles related to metamaterial antennas from 2001 to 2015; this paper overviews some major objectives of such antennas.......The Thomson Reuters Web of Science™ lists more than 1500 journal articles related to metamaterial antennas from 2001 to 2015; this paper overviews some major objectives of such antennas....

  17. 47 CFR 73.753 - Antenna systems.

    Science.gov (United States)

    2010-10-01

    ... 47 Telecommunication 4 2010-10-01 2010-10-01 false Antenna systems. 73.753 Section 73.753... International Broadcast Stations § 73.753 Antenna systems. All international broadcasting stations shall operate with directional antennas. Such antennas shall be designed and operated so that the radiated power...

  18. 47 CFR 95.51 - Antenna height.

    Science.gov (United States)

    2010-10-01

    ... 47 Telecommunication 5 2010-10-01 2010-10-01 false Antenna height. 95.51 Section 95.51... SERVICES General Mobile Radio Service (GMRS) § 95.51 Antenna height. (a) Certain antenna structures used in... this chapter. (b) The antenna for a small base station or for a small control station must not be...

  19. 47 CFR 73.510 - Antenna systems.

    Science.gov (United States)

    2010-10-01

    ... 47 Telecommunication 4 2010-10-01 2010-10-01 false Antenna systems. 73.510 Section 73.510... Noncommercial Educational FM Broadcast Stations § 73.510 Antenna systems. (a) All noncommercial educational... § 73.316 concerning antenna systems contained in subpart B of this part. (b) Directional antenna....

  20. Quantifying mangrove chlorophyll from high spatial resolution imagery

    Science.gov (United States)

    Heenkenda, Muditha K.; Joyce, Karen E.; Maier, Stefan W.; de Bruin, Sytze

    2015-10-01

    Lower than expected chlorophyll concentration of a plant can directly limit photosynthetic activity, and resultant primary production. Low chlorophyll concentration may also indicate plant physiological stress. Compared to other terrestrial vegetation, mangrove chlorophyll variations are poorly understood. This study quantifies the spatial distribution of mangrove canopy chlorophyll variation using remotely sensed data and field samples over the Rapid Creek mangrove forest in Darwin, Australia. Mangrove leaf samples were collected and analyzed for chlorophyll content in the laboratory. Once the leaf area index (LAI) of sampled trees was estimated using the digital cover photography method, the canopy chlorophyll contents were calculated. Then, the nonlinear random forests regression algorithm was used to describe the relationship between canopy chlorophyll content and remotely sensed data (WorldView-2 satellite image bands and their spectral transformations), and to estimate the spatial distribution of canopy chlorophyll variation. The imagery was evaluated at full 2 m spatial resolution, as well as at decreased resampled resolutions of 5 m and 10 m. The root mean squared errors with validation samples were 0.82, 0.64 and 0.65 g/m2 for maps at 2 m, 5 m and 10 m spatial resolution respectively. The correlation coefficient was analyzed for the relationship between measured and predicted chlorophyll values. The highest correlation: 0.71 was observed at 5 m spatial resolution (R2 = 0.5). We therefore concluded that estimating mangrove chlorophyll content from remotely sensed data is possible using red, red-edge, NIR1 and NIR2 bands and their spectral transformations as predictors at 5 m spatial resolution.

  1. Group Delay of High Q Antennas

    DEFF Research Database (Denmark)

    Bahramzy, Pevand; Pedersen, Gert Frølund

    2013-01-01

    become an issue, when working with high Q antennas, because of the steep phase shift over the frequency. In this paper, it is measured how large group delay variations can become, when going from a low Q antenna to a high Q antenna. The group delay of a low Q antenna is shown to be around 1.3 ns, whereas...... a high Q antenna has group delay of around 22 ns. It is due to this huge group delay variation characteristics of high Q antennas, that signal distortion might occur in the radio system with high Q antennas....

  2. Compact Circularly Polarized Patch Antenna Using a Composite Right/Left-Handed Transmission Line Unit-Cell

    Directory of Open Access Journals (Sweden)

    L. Geng

    2013-04-01

    Full Text Available A compact circularly polarized (CP patch antenna using a composite right/left-handed (CRLH transmission line (TL unit-cell is proposed. The CRLH TL unit-cell includes a complementary split ring resonator (CSRR for shunt inductance and a gap loaded with a circular-shaped slot for series capacitance. The CSRR can decrease the TM10 mode resonance frequency, thus reducing the electrical size of the proposed antenna. In addition, the asymmetry of the CSRR brings about the TM01 mode, which can be combined with the TM10 mode by changing the slot radius. The combination of these two orthogonal modes with 90° phase shift makes the proposed antenna provide a CP property. The experimental results show that the proposed antenna has a wider axial ratio bandwidth and a smaller electrical size than the reported CP antennas. Moreover, the proposed antenna is designed without impedance transformer, 90° phase shift, dual feed and ground via.

  3. Multiband Microstrip Antenna for Wi-MAX Application-A study

    OpenAIRE

    Sandip Khakhriya

    2015-01-01

    The wireless revolution is transforming the existing global telecommunications networks into an integrated system providing a broad class of communication services to customers anywhere, anytime in motion or fixed. An antenna is an important device in wireless communication system as its performance will have direct effect on the total system. The continuous shrinking of size of the electronic systems demands small size of antenna elements which can cater the need of multiband ope...

  4. Metal Patch Antenna

    Science.gov (United States)

    Chamberlain, Neil F. (Inventor); Hodges, Richard E. (Inventor); Zawadzki, Mark S. (Inventor)

    2012-01-01

    Disclosed herein is a patch antenna comprises a planar conductive patch attached to a ground plane by a support member, and a probe connector in electrical communication with the conductive patch arranged to conduct electromagnetic energy to or from the conductive patch, wherein the conductive patch is disposed essentially parallel to the ground plane and is separated from the ground plane by a spacing distance; wherein the support member comprises a plurality of sides disposed about a central axis oriented perpendicular to the conductive patch and the ground plane; wherein the conductive patch is solely supported above the ground plane by the support member; and wherein the support member provides electrical communication between the planer conductive patch and the ground plane.

  5. Antenna sunshield membrane

    Science.gov (United States)

    Bogorad, Alexander (Inventor); Bowman, Jr., Charles K. (Inventor); Meder, Martin G. (Inventor); Dottore, Frank A. (Inventor)

    1994-01-01

    An RF-transparent sunshield membrane covers an antenna reflector such as a parabolic dish. The blanket includes a single dielectric sheet of polyimide film 1/2-mil thick. The surface of the film facing away from the reflector is coated with a transparent electrically conductive coating such as vapor-deposited indium-tin oxide. The surface of the film facing the reflector is reinforced by an adhesively attached polyester or glass mesh, which in turn is coated with a white paint. In a particular embodiment of the invention, polyurethane paint is used. In another embodiment of the invention, a layer of paint primer is applied to the mesh under a silicone paint, and the silicone paint is cured after application for several days at room temperature to enhance adhesion to the primer.

  6. Measurement of mobile antenna systems

    CERN Document Server

    Arai, Hiroyuki

    2012-01-01

    If you're involved with the design, installation or maintenance of mobile antenna systems, this thoroughly revised and updated edition of a classic Artech book offers you the most current and comprehensive coverage of all the mandatory measurement techniques you need for your work in the field. This Second Edition presents critical new material in key areas, including radiation efficiency measurement, mobile phone usage position, and MIMO (multiple-input/multiple-output) antennas.This unique resource provides in-depth examinations of all relevant mobile antenna measurement theories, along with

  7. Microstrip and printed antenna design

    CERN Document Server

    Bancroft, Randy

    2009-01-01

    The approach in this book is historical and practical. It covers abasic designsa in more detail than other microstrip antenna books that tend to skip important electrical properties and implementation aspects of these types of antennas. Examples include: quarter-wave patch, quarter by quarter patch, detailed design method for rectangular circularly polarized patch, the use of the TM11 (linear and broadside CP), TM21 (monopole CP pattern) and TM02 (monopole linear) circular patch modes in designs, dual-band antenna designs which allow for independent dual-band frequencies. Limits on broadband m

  8. Absorption Efficiency of Receiving Antennas

    DEFF Research Database (Denmark)

    Andersen, Jørgen Bach; Frandsen, Aksel

    2005-01-01

    A receiving antenna with a matched load will always scatter some power. This paper sets an upper and a lower bound on the absorption efficiency (absorbed power over sum of absorbed and scattered powers), which lies between 0 and 100% depending on the directivities of the antenna and scatter...... patterns. It can approach 100% as closely as desired, although in practice this may not be an attractive solution. An example with a small endfire array of dipoles shows an efficiency of 93%. Several examples of small conical horn antennas are also given, and they all have absorption efficiencies less than...

  9. Science Letters: A modified chlorophyll absorption continuum index for chlorophyll estimation

    Institute of Scientific and Technical Information of China (English)

    YANG Xiao-hua; HUANG Jing-feng; WANG Fu-min; WANG Xiu-zhen; YI Qiu-xiang; WANG Yuan

    2006-01-01

    There is increasing interest in using hyperspectral data for quantitative characterization of vegetation m spatial and temporal scopes. Many spectral indices are being developed to improve vegetation sensitivity by minimizing the background influence. The chlorophyll absorption continuum index (CACI) is such a measure to calculate the spectral continuum on which the analyses are based on the area of the troughs spanned by the spectral continuum. However, different values of CACI were obtained in this method because different positions of continuums were determined by different users. Furthermore, the sensitivity of CACI to agronomic parameters such as green leaf chlorophyll density (GLCD) has been reduced because the fixed positions of continuums are determined when the red edge shifted with the change in GLCD. A modified chlorophyll absorption continuum index (MCACI) is presented in this article. The red edge inflection point (REIP) replaces the maximum reflectance point (MRP) in near-infrared (NIR) shoulder on the CACI continuum. This MCACI has been proved to increase the sensitivity and predictive power of GLCD.

  10. Photochemical reactions of chlorophyll in dehydrated photosystem II: two chlorophyll forms (680 and 700 nm).

    Science.gov (United States)

    Heber, Ulrich; Shuvalov, Vladimir A

    2005-06-01

    Lichens and phototolerant poikilohydric mosses differ from spinach leaves, fern fronds or photosensitive mosses in that they show strongly decreased Fo chlorophyll fluorescence after drying. This desiccation-induced fluorescence loss is rapidly reversible under rehydration. Fluorescence emission from Photosystem II at 685 nm was decreased more strongly by dehydration than 720 nm emission. Reaction centers of Photosystem II lose activity on dehydration and regain it on hydration. Heating of desiccated lichens increased Fo chlorophyll fluorescence. The activation energy for the reversible part of the temperature-dependent fluorescence increase was 0.045 eV, which corresponds to the energy difference between the 680 and 697 nm absorption bands. In desiccated chlorolichens such as Parmelia sulcata, heating induces the appearance of positive variable fluorescence related to the reversible reduction of QA due to overcoming the energy barrier. This is interpreted to provide information on the mechanism of photoprotection: energy is dissipated by changing Chl680 or P680 into a chlorophyll form, which absorbs at 700 nm and emits light at 720 nm (Chl-720 or P680(700)) with a low quantum yield. Dissipation of light energy in this trap is activated by desiccation. PMID:16049759

  11. Rocket Experiment on Construction of Huge Transmitting Antenna for the SPS Using Furoshiki Satellite System with Robots

    Science.gov (United States)

    Kaya, N.; Iwashita, M.; Nakasuka, S.; Summerer, L.; Mankins, J.

    2004-12-01

    Construction technology of huge structures is essential for the future space development as well as the Solar Power Satellite (SPS). The SPS needs huge antennas to transmit the generated electric power toward the ground, while the huge antenna have many useful applications in space as well as on the ground, for example, telecommunication for cellular phones, radars for remote sensing, navigation and observation, and so on. A parabola antenna was mostly used for the space antenna. However, it is very difficult for the larger parabola antenna to keep accuracy of the reflectors and the beam control, because the surfaces of the reflectors are mechanically supported and controlled. The huge space antenna with flexible and ultra-light structures is essential and necessary for the future applications. An active phased array antenna is more suitable and promising for the huge flexible antenna than the parabola antenna. We are proposing to apply the Furoshiki satellite [1] with robots for construction of the huge structures. While a web is deployed using the Furoshiki satellite in the same size of the huge antenna, all of the antenna elements crawl on the web with their own legs toward their allocated locations. We are verifying the deployment concept of the Furoshiki satellite using a sounding rocket with robots crawling on the deployed web. The robots are internationally being developed by NASA, ESA and Kobe University. The paper describes the concept of the crawling robot developed by Kobe University as well as the plan of the rocket experiment.

  12. Metallic post-array loaded cylindrical dielectric resonator antenna

    Directory of Open Access Journals (Sweden)

    Byeong-Yong Park

    2016-01-01

    Full Text Available An investigation of a novel cylindrical dielectric resonator antenna (DRA configuration has been carried out. It is shown that two resonances including the full- and half-cylindrical HE(11δ-like modes can coexist simultaneously at different frequencies by placing a metallic post array in the resonator. Moreover, compared with the conventional HE(11δ mode cylindrical DRA having the same size, the proposed antenna operates in lower frequency band and shows improved bandwidth. The experimental results including the return loss and the radiation patterns are demonstrated.

  13. Electrical properties of spherical dipole antennas with lossy material cores

    DEFF Research Database (Denmark)

    Hansen, Troels Vejle; Kim, Oleksiy S.; Breinbjerg, Olav

    A spherical magnetic dipole antenna with a linear, isotropic, homogenous, passive, and lossy material core is modeled analytically, and closed form expressions are given for the internally stored magnetic and electric energies, the radiation efficiency, and radiation quality factor. This model and...... all the provided expressions are exact and valid for arbitrary core sizes, permeability, permittivity, electric and magnetic loss tangents. Arbitrary dispersion models for both permeability and permittivity can be applied. In addition, we present an investigation for an antenna of fixed electrical...

  14. A NOVEL WIDEBAND ANTENNA DESIGN USING U-SLOT

    Institute of Scientific and Technical Information of China (English)

    Chai Wenwen; Zhang Xiaojuan

    2008-01-01

    U-slot patch antennas with ∏-shaped feed slot are studied, and numerical results based on the FDTD method are presented. The effects of varying physical parameters are investigated with a goal of understanding the coupling among different resonators. It is found that the U-slot patch antenna can be designed to attain 50% impedance bandwidth as well as 30-40% gain bandwidth. By altering the sizes of U-slot and feed slot, the wideband characteristic can be changed into a dual-frequency characteristic.

  15. Semi hemi antenna. [balloon parachuted microwave antenna for stratospheric testing

    Science.gov (United States)

    Repucci, T. A.; Ferris, J. E.

    1978-01-01

    The University of Michigan minipod, which is released from a balloon and floats down on a parachute, is designed for stratospheric testing. The present paper briefly describes the evolution of antenna designs for the minipod 1.5 GHz transceiver, which communicates with and relays information to an aircraft and ground station. The following stages are noted: ordinary monopole, crossed dipole, capacitative antenna, fat monopole, the addition of parasitic elements, and a thinner monopole with taper.

  16. A multifunctional solar panel antenna for cube satellites

    Science.gov (United States)

    Fawole, Olutosin C.

    The basic cube satellite (CubeSat) is a modern small satellite that has a standard size of about one liter (the 1U CubeSat). Three 1U CubeSats could be stacked to form a 3U CubeSat. Their low-cost, short development time, and ease of deployment make CubeSats popular for space research, geographical information gathering, and communication applications. An antenna is a key part of the CubeSat communication subsystem. Traditionally, antennas used on CubeSats are wrapped-up wire dipole antennas, which are deployed after satellite launch. Another antenna type used on CubeSats is the patch antenna. In addition to their low gain and efficiency, deployable dipole antennas may also fail to deploy on satellite launch. On the other hand, a solid patch antenna will compete for space with solar cells when placed on a CubeSat face, interfering with satellite power generation. Slot antennas are promising alternatives to dipole and patch antennas on CubeSats. When excited, a thin slot aperture etched on a conductive sheet (ground plane) is an efficient bidirectional radiator. This open slot antenna can be backed by a reflector or cavity for unidirectional radiation, and solar cells can be placed in spaces on the ground plane not occupied by the slot. The large surface areas of 3U CubeSats can be exploited for a multifunctional antenna by integrating multiple thin slot radiators, which are backed by a thin cavity on the CubeSat surfaces. Solar cells can then be integrated on the antenna surface. Polarization diversity and frequency diversity improve the overall performance of a communication system. Having a single radiating structure that could provide these diversities is desired. It has been demonstrated that when a probe excites a square cavity with two unequal length crossed-slots, the differential radiation from the two slots combines in the far-field to yield circular polarization. In addition, it has been shown that two equal-length proximal slots, when both fed with a

  17. Design of Combined Antenna with Multiple Polarizations

    OpenAIRE

    Zineb Berkat; Noureddine Boukli Hacene; Abdellatif Berkat

    2012-01-01

    In this paper, we present a design of new combined antenna, mixing both linear and circular polarizations, new antenna have to be able to cover several frequency bandwidths, including various radiation properties. From the different researches of antenna with various geometries, and regarding the complexity to combine in a single radiating element several types of polarizations. It is extremely important that the development of antenna used in Wireless Systems. The proposed antenna is simulat...

  18. Electrically floating, near vertical incidence, skywave antenna

    Science.gov (United States)

    Anderson, Allen A.; Kaser, Timothy G.; Tremblay, Paul A.; Mays, Belva L.

    2014-07-08

    An Electrically Floating, Near Vertical Incidence, Skywave (NVIS) Antenna comprising an antenna element, a floating ground element, and a grounding element. At least part of said floating ground element is positioned between said antenna element and said grounding element. The antenna is separated from the floating ground element and the grounding element by one or more electrical insulators. The floating ground element is separated from said antenna and said grounding element by one or more electrical insulators.

  19. Bacteria Foraging Algorithm in Antenna Design

    OpenAIRE

    Biswa Binayak Mangaraj; Manas Ranjan Jena; Saumendra Kumar Mohanty

    2016-01-01

    A simple design procedure to realize an optimum antenna using bacteria foraging algorithm (BFA) is proposed in this paper. The first antenna considered is imaginary. This antenna is optimized using the BFA along with a suitable fitness function formulated by considering some performance parameters and their best values. To justify the optimum design approach, one 12-element Yagi-Uda antenna is considered for an experiment. The optimized result of this antenna obtained using the optimization a...

  20. Electrically-driven optical antennas

    CERN Document Server

    Kern, Johannes; Prangsma, Jord C; Emmerling, Monika; Kamp, Martin; Hecht, Bert

    2015-01-01

    Unlike radiowave antennas, optical nanoantennas so far cannot be fed by electrical generators. Instead, they are driven by light or via optically active materials in their proximity. Here, we demonstrate direct electrical driving of an optical nanoantenna featuring an atomic-scale feed gap. Upon applying a voltage, quantum tunneling of electrons across the feed gap creates broadband quantum shot noise. Its optical frequency components are efficiently converted into photons by the antenna. We demonstrate that the properties of the emitted photons are fully controlled by the antenna architecture, and that the antenna improves the quantum efficiency by up to two orders of magnitude with respect to a non-resonant reference system. Our work represents a new paradigm for interfacing electrons and photons at the nanometer scale, e.g. for on-chip wireless data communication, electrically driven single- and multiphoton sources, as well as for background-free linear and nonlinear spectroscopy and sensing with nanometer...

  1. Circularly-Polarized Microstrip Antenna

    Science.gov (United States)

    Stanton, P. H.

    1985-01-01

    Microstrip construction compact for mobile applications. Circularly polarized microstrip antenna made of concentric cylindrical layers of conductive and dielectric materials. Coaxial cable feedlines connected to horizontal and vertical subelements from inside. Vertical subelement acts as ground for horizontal subelement.

  2. Dual-frequency microwave antenna

    Science.gov (United States)

    Bathker, D. A.; Brunstein, S. A.; Ludwig, A. C.; Potter, P. D.

    1980-01-01

    Single antenna using two feed horns (one for receiving and radiation X-band signals, and one for S-band signals), in conjunction with ellipsoid reflector and dichronic plate, can accommodate two different frequencies simultaneously.

  3. Inflatable Antennas Support Emergency Communication

    Science.gov (United States)

    2010-01-01

    Glenn Research Center awarded Small Business Innovation Research (SBIR) contracts to ManTech SRS Technologies, of Newport Beach, California, to develop thin film inflatable antennas for space communication. With additional funding, SRS modified the concepts for ground-based inflatable antennas. GATR (Ground Antenna Transmit and Receive) Technologies, of Huntsville, Alabama, licensed the technology and refined it to become the world s first inflatable antenna certified by the Federal Communications Commission. Capable of providing Internet access, voice over Internet protocol, e-mail, video teleconferencing, broadcast television, and other high-bandwidth communications, the systems have provided communication during the wildfires in California, after Hurricane Katrina in Mississippi, and following the 2010 Haiti earthquake.

  4. Dipoles, unintentional antennas and EMC

    Directory of Open Access Journals (Sweden)

    Berend Danker

    2008-01-01

    Full Text Available Radiated emissions from equipment commonly originate from electronic circuits that act as electric dipoles created by the signal voltage between the signal conductors or as magnetic dipoles formed by the signal current flowing in a loop. Direct emission is mostly small, but circuits often couple to long conductors or large wiring loops which act as antennas and are efficient radiators. A comparable situation exists when short dipole antennas or small wiring loops receive ambient noise (susceptibility. Usually the amplitude of noise sources or the susceptibility of circuits is an invariable. The dipole strength increases with the distance between the conductors and the area. Shielding and proper grounding decreases the interaction via unintentional antennas. Short-circuiting and the insertion of lossy ferrite cores reduce the efficiency of unintentional antennas.

  5. Scattering Effects of Solar Panels on Space Station Antenna Performance

    Science.gov (United States)

    Panneton, Robert J.; Ngo, John C.; Hwu, Shian U.; Johnson, Larry A.; Elmore, James D.; Lu, Ba P.; Kelley, James S.

    1994-01-01

    Characterizing the scattering properties of the solar array panels is important in predicting Space Station antenna performance. A series of far-field, near-field, and radar cross section (RCS) scattering measurements were performed at S-Band and Ku-Band microwave frequencies on Space Station solar array panels. Based on investigation of the measured scattering patterns, the solar array panels exhibit similar scattering properties to that of the same size aluminum or copper panel mockup. As a first order approximation, and for worse case interference simulation, the solar array panels may be modeled using perfect reflecting plates. Numerical results obtained using the Geometrical Theory of Diffraction (GTD) modeling technique are presented for Space Station antenna pattern degradation due to solar panel interference. The computational and experimental techniques presented in this paper are applicable for antennas mounted on other platforms such as ship, aircraft, satellite, and space or land vehicle.

  6. Concentric Circular Antenna Array Synthesis Using Biogeography Based Optimization

    Directory of Open Access Journals (Sweden)

    Urvinder Singh

    2012-03-01

    Full Text Available Biogeography based optimization (BBO is a new stochastic force based on the science of biogeography. Biogeography is the schoolwork of geographical allotment of biological organisms. BBO utilizes migration operator to share information between the problem solutions. The problem solutions are known as habitats and sharing of features is called migration. In this paper, BBO algorithm is developed to optimize the current excitations of concentric circular antenna arrays (CCAA. Concentric Circular Antenna Array (CCAA has numerous attractive features that make it essential in mobile and communication applications. The goal of the optimization is to reduce the side lobe levels and the primary lobe beam width as much as possible. To confirm the capabilities of BBO, three different CCAA antennas of different sizes are taken. The results obtained by BBO are compared with the Real coded Genetic Algorithm (RGA, Craziness based Particle Swarm Optimization (CRPSO and Hybrid Evolutionary Programming (HEP.

  7. H And U-Slotted Rectangular Microstrip Patch Antenna

    Directory of Open Access Journals (Sweden)

    Bharat Rochani

    2012-09-01

    Full Text Available The microstrip patch is one of the most preferred antenna structures for low cost and compact design for wireless system. Dual and triple band antennas are of a relative interest since they can support multiple communication systems. In this paper we present designs of compact small size microstrip antennas suitable for dual and triple band operations. By loading properly arranged slots on a rectangular microstrip patch, dual and triple frequencies and broadband operations of a single feed rectangular patch is achieved. Dual and triple frequency operation is achieved by loading U and H slots in rectangular patch. The impedance bandwidth of 150MHz, 1.26GHz band for U slot and 154MHz, 484MHz, 396MHz for H slot is obtained in the proposed designs

  8. Effects of biocides on chlorophyll contents of detached basil leaves

    Directory of Open Access Journals (Sweden)

    Titima Arunrangsi

    2013-06-01

    Full Text Available Herbicides and insecticides have been widely and intensively used in agricultural areas worldwide to enhance crop yield. However, many biocides cause serious environmental problems. In addition, the biocides may also have some effects on the treated agricultural crops. To study effects of biocides on chlorophyll content in detached basil leaves, 2,4-D dimethylamine salt (2,4 D-Amine, paraquat, carbosulfan, and azadirachtin, were chosen as representatives of biocide. After applying the chemicals to detached basil leaves overnight in darkness, chlorophyll contents were determined. Only treatment with 2,4 D-Amine resulted in reduction of chlorophyll contents significantly compared to treatment with deionized (DI water. In the case of paraquat and carbosulfan, chlorophyll contents were not significantly changed, while slightly higher chlorophyll contents, compared to DI water, after the treatment with azadirachtin, were observed. The results indicated that 2,4 D-Amine shows an ability to accelerate chlorophyll degradation, but azadirachtin helps to retard chlorophyll degradation, when each biocide is used at the concentration recommended by the manufacturer.

  9. Living antennas on communication satellites

    DEFF Research Database (Denmark)

    Lumholt, Michael

    2003-01-01

    Crises change the global pattern of communication. The communications problems occur because the satellites are optimized to cover specific geographic areas, and these areas cannot be altered once the satellites are in Earth orbit. An effective solution to the problem is to equip communication sa...... satellites with "living" antennas that can adjust their radiation coverage areas according to the new demands. The development of living antennas is, therefore, among the focus areas identified and supported by the European Space Agency, ESA....

  10. Radar techniques using array antennas

    CERN Document Server

    Wirth, Wulf-Dieter

    2013-01-01

    Radar Techniques Using Array Antennas is a thorough introduction to the possibilities of radar technology based on electronic steerable and active array antennas. Topics covered include array signal processing, array calibration, adaptive digital beamforming, adaptive monopulse, superresolution, pulse compression, sequential detection, target detection with long pulse series, space-time adaptive processing (STAP), moving target detection using synthetic aperture radar (SAR), target imaging, energy management and system parameter relations. The discussed methods are confirmed by simulation stud

  11. FINITE ELEMENT ANALYSIS FOR OPTIMIZING ANTENNA FOR MICROWAVE COAGULATION THERAPY

    Directory of Open Access Journals (Sweden)

    MARWAHA S.

    2012-08-01

    Full Text Available Microwave coagulation therapy (MCT is emerging as an attractive modality for thermal therapy of soft tissues targeted in short periods of time, making it particularly suitable for ablation of hepatic and other tumors. In this field of microwave coagulation therapy, the use of minimally invasive antenna is recognized as a very promising technique for the treatment of small tumors because a very thin antenna can be easily inserted inside the body and precisely localized using the advanced 3D imaging techniques and surgical robots. The authors investigated the microwave coaxial antenna operating at 2.45 GHz by varying the slots size for the removal of liver tumor. The analysis was done using 2D finite element modeling. By several optimization steps the antenna is simulated and optimized by comparing the values of specific absorption rate (SAR, mesh statistics and temperature distributions in tissue generated by the antenna with the variations of dimensions of slot from 1 mm to 1.7 mm.

  12. Highly Compact MIMO Antenna System for LTE/ISM Applications

    Directory of Open Access Journals (Sweden)

    Lingsheng Yang

    2015-01-01

    Full Text Available Planar monopole antenna is proposed as the antenna element to form a compact dual-element multiple-input-multiple-output (MIMO antenna system for LTE2300 (used in Asia and Africa and ISM band operation. The system can cover a 310 MHz (2.20–2.51 GHz operating bandwidth, with the total size of 15.5 mm × 18 mm × 1.6 mm. Measured isolation higher than 16 dB is obtained without any specially designed decoupling structures, while the edge-to-edge element spacing is only 7.8 mm (0.08λ at 2.20 GHz. Radiation characteristics, correlation coefficient, and the performance of the whole system with a metal sheet and a plastic housing show this system is competitive for practical MIMO applications. The antenna element is further used to build an eight-element MIMO antenna system; also good results are achieved.

  13. SAR Experiments Using a Conformal Antenna Array Radar Demonstrator

    Directory of Open Access Journals (Sweden)

    Peter Knott

    2012-01-01

    Full Text Available Conformal antenna arrays have been studied for several years but only few examples of applications in modern radar or communication systems may be found up to date due to technological difficulties. The objective of the “Electronic Radar with Conformal Array Antenna” (ERAKO demonstrator system which has been developed at the Fraunhofer Institute for High Frequency Physics and Radar Techniques (FHR is to demonstrate the feasibility of an active electronically scanned antenna for conformal integration into small and medium sized airborne platforms. For practical trials the antenna has been adapted for operation with the Phased Array Multifunctional Imaging Radar (PAMIR system developed at the institute. The antenna in combination with the PAMIR front-end needed to undergo a special calibration procedure for beam forming and imaging post-processing. The present paper describes the design and development of the conformal antenna array of the demonstrator system, its connection to the PAMIR system and results of recently conducted synthetic aperture radar (SAR experiments.

  14. Novel compact asymmetrical fractal aperture Notch band antenna

    Directory of Open Access Journals (Sweden)

    Duvuri S. RAMKIRAN

    2015-12-01

    Full Text Available A compact novel fractal aperture co-planar waveguide fed monopole antenna for multiband applications is proposed in this paper. The structure is asymmetric along the principle axis and seems to be like amoeba shape of radiating element. A band notch characteristic also achieved through this design for communication band applications. The antenna parameters were investigated to fully understand the behaviour and later for the optimisation process. The simulated results through HFSS tool are giving satisfactory results to notch particular band of frequencies and which is giving motivation for the fabrication of the proposed model. All the antenna parameters including S parameters and radiation patterns and current distributions are studied through simulation and experimental validation is done through the proto type modelling on FR4 substrate. Except the Notch band, the proposed antenna model giving excellent radiation characteristics with VSWR less than 2. The prototyped antenna model is occupying a compact size of 18 X 14 X 1.6 mm on FR4 dielectric substrate material with dielectric constant 4.4.

  15. Bandwidth Enhancement Technique of the Meandered Monopole Antenna

    Directory of Open Access Journals (Sweden)

    Chien-Jen Wang

    2015-01-01

    Full Text Available A small dual-band monopole antenna with coplanar waveguide (CPW feeding structure is presented in this paper. The antenna is composed of a meandered monopole, an extended conductor tail, and an asymmetrical ground plane. Tuning geometrical structure of the ground plane excites an additional resonant frequency band and thus enhances the impedance bandwidth of the meandered monopole antenna. Unlike the conventional monopole antenna, the new resonant mode is excited by a slot trace of the CPW transmission line. The radiation performance of the slot mode is as similar as that of the monopole. The parametrical effect of the size of the one-side ground plane on impedance matching condition has been derived by the simulation. The measured impedance bandwidths, which are defined by the reflection coefficient of −6 dB, are 186 MHz (863–1049 MHz, 19.4% at the lower resonant band and 1320 MHz (1490–2810 MHz, 61.3% at the upper band. From the results of the reflection coefficients of the proposed monopole antenna, the operated bandwidths of the commercial wireless communication systems, such as GSM 900, DCS, IMT-2000, UMTS, WLAN, LTE 2300, and LTE 2500, are covered for uses.

  16. Regional ocean-colour chlorophyll algorithms for the Red Sea

    KAUST Repository

    Brewin, Robert J.W.

    2015-05-18

    The Red Sea is a semi-enclosed tropical marine ecosystem that stretches from the Gulf of Suez and Gulf of Aqaba in the north, to the Gulf of Aden in the south. Despite its ecological and economic importance, its biological environment is relatively unexplored. Satellite ocean-colour estimates of chlorophyll concentration (an index of phytoplankton biomass) offer an observational platform to monitor the health of the Red Sea. However, little is known about the optical properties of the region. In this paper, we investigate the optical properties of the Red Sea in the context of satellite ocean-colour estimates of chlorophyll concentration. Making use of a new merged ocean-colour product, from the European Space Agency (ESA) Climate Change Initiative, and in situ data in the region, we test the performance of a series of ocean-colour chlorophyll algorithms. We find that standard algorithms systematically overestimate chlorophyll when compared with the in situ data. To investigate this bias we develop an ocean-colour model for the Red Sea, parameterised to data collected during the Tara Oceans expedition, that estimates remote-sensing reflectance as a function of chlorophyll concentration. We used the Red Sea model to tune the standard chlorophyll algorithms and the overestimation in chlorophyll originally observed was corrected. Results suggest that the overestimation was likely due to an excess of CDOM absorption per unit chlorophyll in the Red Sea when compared with average global conditions. However, we recognise that additional information is required to test the influence of other potential sources of the overestimation, such as aeolian dust, and we discuss uncertainties in the datasets used. We present a series of regional chlorophyll algorithms for the Red Sea, designed for a suite of ocean-colour sensors, that may be used for further testing.

  17. Investigation of Aperture Coupled Microstrip Antenna to Obtain a High Efficient Active Integrated Antenna by Using Class F and Inverse Class F Power Amplifiers

    OpenAIRE

    Liu, Lei

    2013-01-01

    In wireless communications and radar systems, there are requirements for high efficiency, small size, low cost, and wide bandwidth of transmitter front –end usage for commercial and also military applications. Active integrated antenna (AIA) could satisfy almost all the requirements. The overall objective of the proposed research is to model, optimise, and design a compact and high efficient AIA using an aperture coupled microstrip antenna (ACMA) by integrating with a power amplifier (PA). Re...

  18. Development of film antenna for diversity reception; Diversity taio film antenna no kaihatsu

    Energy Technology Data Exchange (ETDEWEB)

    Shigeta, K.; Taniguchi, T.; Kubota, K. [Mazda Motor Corp., Hiroshima (Japan)

    1997-10-01

    Based on the principle of capacitance-loaded window antennas, a new film antenna construction pasting an antenna element on a defogger element printed on a rear window was found. The film antennas show high reception performance, and can be used as television diversity antennas or a VICS-FM multiplex antenna. This paper describes the antenna design concept, the antenna construction and the application to a recreational vehicle which styling is 1.3-Box wagon for the electric accessory. 2 refs., 11 figs.

  19. Photoinduced electron transfer of chlorophyll in lipid bilayer system

    Indian Academy of Sciences (India)

    D K Lee; K W Seo; Y S Kang

    2002-12-01

    Photoinduced electron transfer from chlorophyll- through the interface of dipalmitoylphosphatidylcholine (DPPC) headgroup of the lipid bilayers was studied with electron magnetic resonance (EMR). The photoproduced radicals were identified with electron spin resonance (ESR) and radical yields of chlorophyll- were determined by double integration ESR spectra. The formation of vesicles was identified by changes in measured max values from diethyl ether solutions to vesicles solutions indirectly, and observed directly with SEM and TEM images. The efficiency of photosynthesis in model system was determined by measuring the amount of chlorophyll-a radical yields which were obtained from integration of ESR spectra.

  20. Chlorophyll derivatives for pest and disease control: Are they safe?

    Energy Technology Data Exchange (ETDEWEB)

    Azizullah, Azizullah, E-mail: azizswabi@gmail.com; Murad, Waheed

    2015-01-15

    Chlorophyll derivatives are getting widespread acceptance among the researchers as natural photosensitizers for photodynamic control of pests and disease vectors; however, rare attention has been given to evaluation of their toxicity to non-target organisms in the environment. This perspective article highlights that chlorophyll derivatives may not be as safe as believed and can possibly pose risk to non-target organisms in the environment. We invite the attention of environmental biologists, particularly ecotoxicologists, to contribute their role in making the application of chlorophyll derivatives more environmentally friendly and publicly acceptable.

  1. Chlorophyll derivatives for pest and disease control: Are they safe?

    International Nuclear Information System (INIS)

    Chlorophyll derivatives are getting widespread acceptance among the researchers as natural photosensitizers for photodynamic control of pests and disease vectors; however, rare attention has been given to evaluation of their toxicity to non-target organisms in the environment. This perspective article highlights that chlorophyll derivatives may not be as safe as believed and can possibly pose risk to non-target organisms in the environment. We invite the attention of environmental biologists, particularly ecotoxicologists, to contribute their role in making the application of chlorophyll derivatives more environmentally friendly and publicly acceptable

  2. Inkjet Printing of Paper-Based Wideband and High Gain Antennas

    KAUST Repository

    Cook, Benjamin

    2011-12-07

    This thesis represents a major contribution to wideband and high gain inkjet-printed antennas on paper. This work includes the complete characterization of the inkjet printing process for passive microwave devices on paper substrate as well as several ultra-wideband and high gain antenna designs. The characterization work includes the electrical characterization of the permittivity and loss tangent for paper substrate through 10 GHz, ink conductivity data for variable sintering conditions, and minimum feature sizes obtainable by today’s current inkjet processes for metallic nanoparticles. For the first time ever, inkjet-printed antennas are demonstrated that operate over the entire UWB band and demonstrate gains up to 8dB. This work also presents the first fractal-based inkjet-printed antennas with enhanced bandwidth and reduced production costs, and a novel slow wave log periodic dipole array which shows minimizations of 20% in width over conventional log periodic antennas.

  3. Design of a Miniaturized Meandered Line Antenna for UHF RFID Tags.

    Science.gov (United States)

    Rokunuzzaman, Md; Islam, Mohammad Tariqul; Rowe, Wayne S T; Kibria, Salehin; Jit Singh, Mandeep; Misran, Norbahiah

    2016-01-01

    A semi-circle looped vertically omnidirectional radiation (VOR) patterned tag antenna for UHF (919-923 MHz for Malaysia) frequency is designed to overcome the impedance mismatch issue in this paper. Two impedance matching feeding strips are used in the antenna structure to tune the input impedance of the antenna. Two dipole shaped meandered lines are used to achieve a VOR pattern. The proposed antenna is designed for 23-j224 Ω chip impedance. The antenna is suitable for 'place and tag' application. A small size of 77.68×35.5 mm2 is achieved for a read range performance of 8.3 meters using Malaysia regulated maximum power transfer of 2.0 W effective radiated power (ERP). PMID:27533470

  4. Method of measuring the amplitude directivity pattern of parabolic mirrored antennas in the audio frequency range

    Directory of Open Access Journals (Sweden)

    Sadchenko A. V.

    2016-02-01

    Full Text Available Directivity pattern (DP or graphical representation of the dependence of gain factor (directivity gain of antennas on the direction of the antenna in the target plane is the main characteristic that describes its directional properties. Running DP measurements directly in the microwave range is very expensive. While generating and receiving devices for the acoustic frequency range are reasonably priced. In this paper, we propose a method for measuring the amplitude directivity pattern of parabolic mirrored antennas on the basis of sound equivalent, which is based on the identity of the numerical values of the directivity gain of microwave range, and at audio frequencies. The paper presents analytical expressions for the calculation of equivalent frequency and defines the requirements for the minimum size of the antenna. The paper contains a modified block diagram for an amplitude directivity pattern meter for parabolic mirrored antennas in the audio frequency range.

  5. CPW fed Inverted U-Shape Microstrip Patch Antenna for WLAN/WiMAX Applications

    Directory of Open Access Journals (Sweden)

    Pradeep Kumar

    2014-01-01

    Full Text Available A coplanar waveguide (CPW-fed planar monopole antenna for WiMAX and WLAN applications is presented. The antenna, which occupies a small size, is simply composed of an inverted U-shaped radiating patch with E-shape slot. By carefully selecting the positions of this slot, reasonable bandwidth of the antenna can be obtained so that operating bands covering 2.4/5.2/5.8 GHz WLAN bands and the 2.5/3.5/5.5 GHz WiMAX bands. The measured results also demonstrate that the proposed antenna has appreciable bandwidth and is thus suitable to be integrated within the portable devices for WiMAX/WLAN applications. The various characteristics parameters like S-parameter, VSWR and radiation pattern are studied. The proposed antenna is simulated by using ANSOFT HFSS software

  6. CPW-fed Wideband Antenna with U-shaped Ground Plane

    Directory of Open Access Journals (Sweden)

    Shagun Maheshwari

    2014-11-01

    Full Text Available This paper proposes the design of CPW-fed wideband antenna with U-shaped ground plane. The proposed antenna is a simple printed antenna, which is fed by a 50Ω CPW line. The Antenna has a compact size of 13mm×25mm. To obtain wide bandwidth, a slot is cut in ground plane and radiating patch is modified. The proposed antenna yields the operating frequency range from 7.3GHz to 15.1GHz, which offers the bandwidth of 7.79GHz. Simulation has been performed by using CST Microwave Studio Software. This frequency range satisfies the system requirements for Narrowband PCS Services, Satellite, Cellular Phone, Domestic Public Land Mobile Communication and International Public Broadcasting applications.

  7. Low Profile Tunable Dipole Antenna Using BST Varactors for Biomedical Applications

    Science.gov (United States)

    Cure, David; Weller, Thomas M.; Miranda, Felix A.; Price, Tony

    2013-01-01

    In this paper a 2.4 GHz low profile (lambda/47) tunable dipole antenna is evaluated in the presence of a human core model (HCM) body phantom. The antenna uses a frequency selective surface (FSS) with interdigital barium strontium titanate (BST) varactor-tuned unit cells and its performance is compared to a similar low profile antenna that uses an FSS with semiconductor varactor diodes. The measured data of the antenna demonstrate tunability from 2.2 GHz to 2.55 GHz in free space and impedance match improvement in the presence of a HCM at different distances. This antenna has smaller size, lower cost and less weight compared to the semiconductor varactor diode counterpart.

  8. Low Profile Tunable Dipole Antennas Using BST Varactors for Biomedical Applications

    Science.gov (United States)

    Cure, David; Weller, Thomas; Price, Tony; Miranda, Felix A.

    2013-01-01

    In this presentation a 2.4 GHz low profile (lambda45) tunable dipole antenna is evaluated in the presence of a human core model (HCM) body phantom. The antenna uses a frequency selective surface (FSS) with interdigital barium strontium titanate (BST) varactor-tuned unit cells and its performance is compared to a similar low profile antenna that uses an FSS with semiconductor varactor diodes. The measured data of the antenna demonstrate tunability from 2.2 GHz to 2.55 GHz in free space and impedance match improvement in the presence of a HCM at different distances. This antenna has smaller size, lower cost and less weight compared to the semiconductor varactor diode counterpart.

  9. A TRIBAND SWASTIKA SHAPED PATCH ANTENNA WITH REDUCED MUTUAL COUPLING FOR WIRELESS MIMO SYSTEMS

    Institute of Scientific and Technical Information of China (English)

    K Jagadeesh Babu; K Sri Ramakrishna; L Pratap Reddy

    2011-01-01

    A novel compact Swastika shaped patch antenna is designed in the present work,which can be used for Multiple Input Multiple Output (MIMO) systems.The proposed two element MIMO system resonates at a triband of 3.3 GHz,5.8 GHz,and 7.1 GHz with an improved impedance bandwidth of 37% and a reduced mutual coupling of -33 dB.These results are better compared to a normal E shaped patch antenna designed with same size and thickness,achieved without using any additional decoupling methods.A 2 × 2 MIMO system employing the Swastika shaped patch antennas is analyzed using computational electromagnetic ray tracing software for an indoor environment.The results show an improvement in the capacity compared to a 2 × 2 MIMO system developed with dipole antennas.The proposed antenna is a good choice for MIMO systems operating for several Ultra WideBand (UWB) applications.

  10. Enhanced infrared spectroscopy using small-gap antennas prepared with two-step evaporation nanosphere lithography.

    Science.gov (United States)

    Hoffmann, Jón Mattis; Janssen, Hendrik; Chigrin, Dmitry N; Taubner, Thomas

    2014-06-16

    We use nanosphere lithography in combination with two evaporation steps to create bow-tie like infrared antennas with small gaps. The angle of the sample with respect to the evaporation source is changed between two evaporation steps resulting in a displacement of the respective antenna arrays and, therefore, in decreased antenna-gaps. Furthermore, we demonstrate the gap-dependency of surface-enhanced infrared absorption (SEIRA) spectroscopy using the absorption band of the natural SiO(2)-layer of the silicon substrate and antennas with different gap size. A multi-oscillator-model is used to describe the Fano-like spectral coupling of the antenna resonances with the SiO(2) absorption band. PMID:24977539

  11. Design and Analysis of Compact Coplanar Wave Guide Fed Asymmetric Monopole Antennas

    Directory of Open Access Journals (Sweden)

    B.T.P. Madhav

    2015-05-01

    Full Text Available A compact CPW-FED monopole antenna for wireless communication applications is presented in this study. The proposed antenna models consisting of very compact size of 27.5×13 mm on RT-Duroid substrate of εr = 2.2 with thickness of 1.6 mm. The proposed antenna structures cover the frequency bands of C and Ku. In addition, the antenna exhibits monopole like radiation characteristics and good antenna gain of more than 1.6 dB in c-band and 2.79 dB in Ku-band, which is suitable to integrate with the devices for wireless communication devices for communication system applications.

  12. Imaging individual proteins and nanodomains on intact cell membranes with a probe-based optical antenna.

    Science.gov (United States)

    van Zanten, Thomas S; Lopez-Bosque, Maria J; Garcia-Parajo, Maria F

    2010-01-01

    Optical antennas that confine and enhance electromagnetic fields in a nanometric region hold great potential for nanobioimaging and biosensing. Probe-based monopole optical antennas are fabricated to enhance fields localized to antenna apex in aqueous conditions. These probes are used under appropriate excitation antenna conditions to image individual antibodies with an unprecedented resolution of 26 +/- 4 nm and virtually no surrounding background. On intact cell membranes in physiological conditions, the obtained resolution is 30 +/- 6 nm. Importantly, the method allows individual proteins to be distinguished from nanodomains and the degree of clustering to be quantified by directly measuring physical size and intensity of individual fluorescent spots. Improved antenna geometries should lead to true live cell imaging below 10-nm resolution with position accuracy in the subnanometric range. PMID:19943247

  13. Computer Aided Design and Simulation of a Multiobjective Microstrip Patch Antenna for Wireless Applications

    Directory of Open Access Journals (Sweden)

    Chitra Singh

    2011-03-01

    Full Text Available The utility and attractiveness of microstrip antennas has made it ever more important to find ways to precisely determine the radiation patterns of these antennas. Taking benefit of the added processing power of today’s computers, electromagnetic simulators are emerging to perform both planar and 3D analysis of high-frequency structures. One such tool studied was IE3D, which is a program that utilizes method of moment. This paper makes an investigation of the method used by the program, and then uses IE3D software to construct microstrip antennas and analyze the simulation results. The antenna offers good electrical performance and at the same time preserves the advantages of microstrip antennas such as small size, easy to manufacture as no lumped components are employed in the design and thus, is low cost; and most importantly, it serves multiple wireless applications.

  14. E-Textile Antennas for Space Environments

    Science.gov (United States)

    Kennedy, Timothy F.; Fink, Patrick W.; Chu, Andrew W.

    2007-01-01

    The ability to integrate antennas and other radio frequency (RF) devices into wearable systems is increasingly important as wireless voice, video, and data sources become ubiquitous. Consumer applications including mobile computing, communications, and entertainment, as well as military and space applications for integration of biotelemetry, detailed tracking information and status of handheld tools, devices and on-body inventories are driving forces for research into wearable antennas and other e-textile devices. Operational conditions for military and space applications of wireless systems are often such that antennas are a limiting factor in wireless performance. The changing antenna platform, i.e. the dynamic wearer, can detune and alter the radiation characteristics of e-textile antennas, making antenna element selection and design challenging. Antenna designs and systems that offer moderate bandwidth, perform well with flexure, and are electronically reconfigurable are ideally suited to wearable applications. Several antennas, shown in Figure 1, have been created using a NASA-developed process for e-textiles that show promise in being integrated into a robust wireless system for space-based applications. Preliminary characterization of the antennas with flexure indicates that antenna performance can be maintained, and that a combination of antenna design and placement are useful in creating robust designs. Additionally, through utilization of modern smart antenna techniques, even greater flexibility can be achieved since antenna performance can be adjusted in real-time to compensate for the antenna s changing environment.

  15. Changes of Photosystem Ⅱ Electron Transport in the Chlorophyll-deficient Oilseed Rape Mutant Studied by Chlorophyll Fluorescence and Thermoluminescence

    Institute of Scientific and Technical Information of China (English)

    Jun-Wei Guo; Jin-Kui Guo; Yun Zhao; Lin-Fang Du

    2007-01-01

    The photosystem Ⅱ (PSII) complex of photosynthetic membranes comprises a number of chlorophyll-binding proteins that are important to the electron flow. Here we report that the chlorophyll b-deficient mutant has de creased the amount of light-harvesting complexes with an increased amount of some core polypeptides of PSII,including CP43 and CP47. By means of chlorophyll fluorescence and thermoluminescence, we found that the ratio of Fv/Fm, qP and electron transport rate in the chlorophyll b-deficient mutant was higher compared to the wild type.In the chlorophyll b-deficient mutant, the decay of the primary electron acceptor quinones (QA-) reoxidation was decreased, measured by the fluorescence. Furthermore, the thermolumlnescence studies in the chlorophyll b deficient mutant showed that the B band (S2/S3QB-) decreased slightly and shifted up towards higher temperatures.In the presence of dichlorophenyl-dimethylurea, which is inhibited in the electron flow to the second electron acceptor quinines (QB) at the PSII acceptor side, the maximum of the Q band (S2QA-) was decreased slightly and shifted down to lower temperatures, compared to the wild type. Thus, the electron flow within PSll of the chlorophyll b-deficient mutant was down-regulated and characterized by faster oxidation of the primary electron acceptor quinine QA- via forward electron flow and slower reduction of the oxidation S states.

  16. Remote sensing of chlorophyll fluorescence with GOSAT

    Science.gov (United States)

    Somkuti, Peter; Boesch, Hartmut; Parker, Robert

    2015-04-01

    Sun-induced chlorophyll fluorescence (Fs) emitted by plants as a by-product during photosynthesis carries information about their photosynthetic activity. It is possible to exploit space-based remote sensing measurements to retrieve the fluorescence signal and thus indirectly study carbon fluxes on a global scale. We implement a fluorescence retrieval based on the method pioneered by Frankenberg et al. (2011) into the framework of the University of Leicester Full-Physics GOSAT CO2 retrieval (UoL-FP). This physically-based approach is applied to high-resolution spectra at the edges of the O2 A-Band in the red to NIR range, that feature strong solar as well as a few weak O2 absorption lines. The fluorescence signal, which acts as an additional source, results in an in-filling of the measured solar absorption lines that are used to distinguish Fs from reflectance effects. By analysing GOSAT soundings from 2009 onwards, we examine global and regional long-term trends of Fs and compare them with parameters related to plant physiology, such as spectral vegetation indices and MODIS-derived model GPP values. Following Guanter et al. (2012) and Frankenberg et al. (2011), different regions and biomes are considered and we find that seasonal trends of both model GPP data as well as greenness indicators are well reproduced by our GOSAT-retrieved Fs.

  17. Photogeneration of charges in microcrystalline chlorophyll a

    Energy Technology Data Exchange (ETDEWEB)

    Kassi, Hassan [Scientech R and D, Inc., 2200 Rue Didbec S., Bureau 203, Trois-Rivieres, Trois-Rivieres, QC, G8Z 4H1 (Canada); Barazzouk, Said, E-mail: barazzos@uqtr.c [Groupe de Recherche en Biologie Vegetale, Universite du Quebec a Trois-Rivieres, Trois-Rivieres, QC, G9A 5H7 (Canada); Brullemans, Marc [Groupe de Recherche en Biologie Vegetale, Universite du Quebec a Trois-Rivieres, Trois-Rivieres, QC, G9A 5H7 (Canada); Leblanc, Roger M. [Department of Chemistry, University of Miami, P.O. Box 249118, Coral Gables, FL 33124-0431 (United States); Hotchandani, Surat [Groupe de Recherche en Biologie Vegetale, Universite du Quebec a Trois-Rivieres, Trois-Rivieres, QC, G9A 5H7 (Canada)

    2010-07-01

    The electric-field and temperature dependence of hole photogeneration in chlorophyll a (Chla) have been analyzed in terms of electric-field assisted thermal dissociation of charge pairs based on Onsager theory. An excellent agreement between the experimental and theoretical values of the slope-to-intercept ratio, S/I, for the plot of photogeneration efficiency vs. electric field at low field strengths provides a proof for the applicability of the Onsager approach to the photogeneration of charges in Chla. A value of 19 nm has been obtained for Coulomb capture radius, r{sub c}, from S/I. From the temperature dependence of photogeneration, the initial separation, r{sub 0}, of photogenerated electron-hole has been evaluated, and has a value of 1.24 nm. This smaller r{sub 0} compared to r{sub c} leads to a feeble dissociation probability of electron-hole pairs into free carriers, and may, among other factors, explain the low power conversion efficiencies of Chla photovoltaic cells.

  18. Co-design of on-chip antennas and circuits for a UNII band monolithic transceiver

    KAUST Repository

    Shamim, Atif

    2012-07-28

    The surge of highly integrated and multifunction wireless devices has necessitated the designers to think outside the box for solutions that are unconventional. The new trends have provided the impetus for low cost and compact RF System-on-Chip (SoC) approaches [1]. The major advantages of SoC are miniaturization and cost reduction. A major bottleneck to the true realization of monolithic RF SoC transceivers is the implementation of on-chip antennas with circuitry. Though complete integrated transceivers with on-chip antennas have been demonstrated, these designs are generally for high frequencies. Moreover, they either use non-standard CMOS processes or additional fabrication steps to enhance the antenna efficiency, which in turn adds to the cost of the system [2-3]. Another challenge related to the on-chip antennas is the characterization of their radiation properties. Most of the recently reported work (summarized in Table I) shows that very few on-chip antennas are characterized. Our previous work [4], demonstrated a Phase Lock Loop (PLL) based transmitter (TX) with an on-chip antenna. However, the radiation from the on-chip antenna experienced strong interference due to 1) some active circuitry on one side of the chip and 2) the PCB used to mount the chip in the anechoic chamber. This paper presents, for the first time, a complete 5.2 GHz (UNII band) transceiver with separate TX and receiver (RX) antennas. To the author\\'s best knowledge, its size of 3 mm2 is the smallest reported for a UNII band transceiver with two on-chip antennas. Both antennas are characterized for their radiation properties through an on-wafer custom measurement setup. The strategy to co-design on-chip antennas with circuits, resultant trade-offs and measurement challenges have also been discussed. © 2010 IEEE.

  19. Photon-blockade as protection in photosynthesis Antenna with cyclic structures

    CERN Document Server

    Dong, Hui; Yi, Zhenhuan; Agarwal, Girish S; Scully, Marlan O

    2016-01-01

    Excess energy absorbed by the light-harvesting antennas could be potentially harmful to the photosynthesis complexes. The biological system has developed various mechanisms, e.g. non-photon chemical quenching, to prevent these damages by dissipating energy into the surrounding environment. In additional to this well-known mechanism, we hypothesise a new protection mechanism of suppressing the probability of double excitation in photosynthesis system, where pigment-protein complexes form cyclic structures with dipole-dipole interaction between adjacent chlorophylls. We also demonstrate robustness of the photon blockade against the disorder in the ring structures. The photon blockade can explain the recent observation on the suppression of simultaneous emission of two photons in natural photosynthetic antennas.

  20. Quenching action of monofunctional sulfur mustard on chlorophyll fluorescence: towards an ultrasensitive biosensor.

    Science.gov (United States)

    Kaur, Simerjit; Singh, Minni; Flora, Swaran Jeet Singh

    2013-11-01

    An ultrasensitive fluorimetric biosensor for the detection of chemical warfare agent sulfur mustard (SM) was developed using its monofunctional analogue. SM is a vesicant and a potent chemical threat owing to its direct toxic effects on eyes, lungs, skin and DNA. This work investigates the quenching action of the analyte on chlorophyll fluorescence as elucidated by nuclear magnetic resonance, Fourier transform infrared spectroscopy and mass spectrometry studies suggesting the electrophilic attack of carbonium ion on nitrogens of the porphyrin moiety of chlorophyll. The properties of immobilisation matrix were optimised and scanning electron microscope observations confirmed improvement in pore size of sol-gels by addition of 32 % (v/v) glycerol, a feature enabling enhanced sensitivity towards the analyte. Chlorophyll embedded sol-gel was treated with increasing concentrations of monofunctional SM and the corresponding drop in maximum fluorescence intensity as measured by emission at 673 nm was observed, which varied linearly and had a detection limit of 7.68 × 10(-16) M. The biosensor was found to be 6 orders of magnitude more sensitive than the glass microfibre-based disc biosensor previously reported by us. PMID:23955347

  1. Antenna Miniaturization with MEMS Tunable Capacitors

    DEFF Research Database (Denmark)

    Barrio, Samantha Caporal Del; Morris, Art; Pedersen, Gert Frølund

    2014-01-01

    In today’s mobile device market, there is a strong need for efficient antenna miniaturization. Tunable antennas are a very promising way to reduce antenna volume while enlarging its operating bandwidth. MEMS tunable capacitors are state-ofthe- art in terms of insertion loss and their characterist......In today’s mobile device market, there is a strong need for efficient antenna miniaturization. Tunable antennas are a very promising way to reduce antenna volume while enlarging its operating bandwidth. MEMS tunable capacitors are state-ofthe- art in terms of insertion loss and their...

  2. Vehicle antenna development for mobile satellite applications

    Science.gov (United States)

    Woo, K.

    1988-01-01

    The paper summarizes results of a vehicle antenna program at JPL in support of a developing U.S. mobile satellite services (MSS) designed to provide telephone and data services for the continental United States. Two classes of circularly polarized vehicle antennas have been considered for the MSS: medium-gain, satellite-tracking antennas with 10-12-dBic gain; and low-gain, azimuthally omnidirectional antennas with 3-5-dBic gain. The design and performance of these antennas are described, and the two antennas are shown to have peculiar advantages and disadvantages.

  3. Modern lens antennas for communications engineering

    CERN Document Server

    Thornton, John

    2012-01-01

    The aim of this book is to present the modern design principles and analysis of lens antennas. It gives graduates and RF/Microwave professionals the design insights in order to make full use of lens antennas.  Why do we want to write a book in lens antennas? Because this topic has not been thoroughly publicized, its importance is underestimated. As antennas play a key role in communication systems, recent development in wireless communications would indeed benefit from the characteristics of lens antennas: low profile, and low cost etc.  The major advantages of lens antennas are na

  4. Systems analysis for DSN microwave antenna holography

    Science.gov (United States)

    Rochblatt, D. J.

    1989-01-01

    Proposed systems for Deep Space Network (DSN) microwave antenna holography are analyzed. Microwave holography, as applied to antennas, is a technique which utilizes the Fourier Transform relation between the complex far-field radiation pattern of an antenna and the complex aperture field distribution to provide a methodology for the analysis and evaluation of antenna performance. Resulting aperture phase and amplitude distribution data are used to precisely characterize various crucial performance parameters, including panel alignment, subreflector position, antenna aperture illumination, directivity at various frequencies, and gravity deformation. Microwave holographic analysis provides diagnostic capacity as well as being a powerful tool for evaluating antenna design specifications and their corresponding theoretical models.

  5. Single Band Helical Antenna in Axial Mode

    Directory of Open Access Journals (Sweden)

    Parminder Singh

    2012-11-01

    Full Text Available Helical antennas have been widely used in a various useful applications, due to their low weight and low profile conformability, easy and cheap realization.Radiation properties of this antenna are examined both theoretically and experimentally. In this paper, an attempt has been made to investigate new helical antenna structure for Applications. CST MWS Software is used for the simulation and design calculations of the helical antennas. The axial ratio, return loss, VSWR, Directivity, gain, radiation pattern is evaluated. Using CST MWS simulation software proposed antenna is designed/simulated and optimized. The antenna exhibits a single band from 0 GHz to 3 GHz for GPS and several satellite applications

  6. Broadband Multilayered Array Antenna with EBG Reflector

    Directory of Open Access Journals (Sweden)

    P. Chen

    2013-01-01

    Full Text Available Most broadband microstrip antennae are implemented in the form of slot structure or laminate structure. The impedance bandwidth is broadened, but meanwhile, the sidelobe of the directivity pattern and backlobe level are enlarged. A broadband stacked slot coupling microstrip antenna array with EBG structure reflector is proposed. Test results indicate that the proposed reflector structure can effectively improve the directivity pattern of stacked antenna and aperture coupled antenna, promote the front-to-back ratio, and reduce the thickness of the antenna. Therefore, it is more suitable to be applied as an airborne antenna.

  7. Antenna for passive RFID tags

    Science.gov (United States)

    Schiopu, Paul; Manea, Adrian; Cristea, Ionica; Grosu, Neculai; Vladescu, Marian; Craciun, Anca-Ileana; Craciun, Alexandru

    2015-02-01

    Minuscule devices, called RFID tags are attached to objects and persons and emit information which positioned readers may capture wirelessly. Many methods of identification have been used, but that of most common is to use a unique serial number for identification of person or object. RFID tags can be characterized as either active or passive [1,2]. Traditional passive tags are typically in "sleep" state until awakened by the reader's emitted field. In passive tags, the reader's field acts to charge the capacitor that powers the badge and this can be a combination of antenna and barcodes obtained with SAW( Surface Acoustic Wave) devices [1,2,3] . The antenna in an RFID tag is a conductive element that permits the tag to exchange data with the reader. The paper contribution are targeted to antenna for passive RFID tags. The electromagnetic field generated by the reader is somehow oriented by the reader antenna and power is induced in the tag only if the orientation of the tag antenna is appropriate. A tag placed orthogonal to the reader yield field will not be read. This is the reason that guided manufacturers to build circular polarized antenna capable of propagating a field that is alternatively polarized on all planes passing on the diffusion axis. Passive RFID tags are operated at the UHF frequencies of 868MHz (Europe) and 915MHz (USA) and at the microwave frequencies of 2,45 GHz and 5,8 GHz . Because the tags are small dimensions, in paper, we present the possibility to use circular polarization microstrip antenna with fractal edge [2].

  8. Relationship between chlorophyll-a and column primary production

    Digital Repository Service at National Institute of Oceanography (India)

    Dalal, S.G.; Bhargava, R.M.S.

    Relationship between surface chlorophyll a and column primary production has been established to help in estimating the latter more quickly and accurately. The equation derived is Primary Production, y = 0.54 Ln Chl a - 0.6. The relationship...

  9. Assessment of water pollution by airborne measurement of chlorophyll

    Science.gov (United States)

    Arvesen, J. C.; Weaver, E. C.; Millard, J. P.

    1972-01-01

    Remote measurement of chlorophyll concentrations to determine extent of water pollution is discussed. Construction and operation of radiometer to provide measurement capability are explained. Diagram of equipment is provided.

  10. Remote sensing of tidal chlorophyll-a variations in estuaries

    Science.gov (United States)

    Catts, Glenn P.; Khorram, Siamak; Cloern, James E.; Knight, Allen W.; Degloria, Stephen D.

    1985-01-01

    Simultaneous acquisition of surface chlorophyll-a concentrations for 39 samples from boats and Daedalus 1260 Multispectral Scanner data from a U-2 aircraft was conducted in the northern reaches of San Francisco Bay on 28 August 1980. These data were used to develop regression models for predicting surface chlorophyll-a concentrations over the study area for ebb-tide (8.40 a.m. P.D.T. (Pacific Daylight Time)) and flood-tide (3.10 p.m. P.D.T.) conditions. After selection of a single ‘best fitting’ model for both morning and afternoon data sets, the chlorophyll-a concentration was predicted for ebb and flood tide for the entire study area at approximately 40m × 40m resolution. The predicted spatial display of chlorophyll-a revealed a localized area of high phytoplankton biomass that has been inferred from field surveys and appears to be a common summer phenomenon.

  11. L-band compact printed quadrifilar helix antenna with ‘Iso-Flux' radiating pattern for stratospheric balloons telemetry

    OpenAIRE

    Fonseca, Nelson; Hebib, Sami; Aubert, Hervé

    2008-01-01

    International audience Two sinusoidal profile compact printed quadrifilar helix antennas have been presented. Particular care has been given to the co and cross-polarization patterns during the parametric design process to produce antennas with performances very similar to the conventional one in those aspects. A size reduction ranging from 30 to 40% is confirmed. Experimental validation will be presented at the conference.

  12. A CSRR-Fed SIW Cavity-Backed Fractal Patch Antenna for Wireless Energy Harvesting and Communication.

    Science.gov (United States)

    Cao, Hailin; Jiang, Fen; Liu, Jiujiu; Cai, Wenbin; Tang, Mingchun; Tan, Xiaoheng; Yang, Shizhong

    2015-01-01

    This paper presents a novel compact dual-band and dual-polarized complementary split-ring resonator (CSRR)-fed substrate-integrated waveguide (SIW) cavity-backed fractal patch antenna for wireless energy harvesting and communication. The proposed antenna is composed of a Giuseppe Peano fractal radiation patch with a backed SIW cavity. To enhance the bandwidth and minimize the dimensions, the CSRR structure is designed to feed the Giuseppe Peano fractal patch orthogonally. A prototype of the proposed antenna is simulated, fabricated and measured. The proposed antenna exhibits good directionality and high cross-polarization level with especially compact size. PMID:26343663

  13. A CSRR-Fed SIW Cavity-Backed Fractal Patch Antenna for Wireless Energy Harvesting and Communication

    Directory of Open Access Journals (Sweden)

    Hailin Cao

    2015-08-01

    Full Text Available This paper presents a novel compact dual-band and dual-polarized complementary split-ring resonator (CSRR-fed substrate-integrated waveguide (SIW cavity-backed fractal patch antenna for wireless energy harvesting and communication. The proposed antenna is composed of a Giuseppe Peano fractal radiation patch with a backed SIW cavity. To enhance the bandwidth and minimize the dimensions, the CSRR structure is designed to feed the Giuseppe Peano fractal patch orthogonally. A prototype of the proposed antenna is simulated, fabricated and measured. The proposed antenna exhibits good directionality and high cross-polarization level with especially compact size.

  14. Design of Vivaldi antenna array with end-fire beam steering function for 5G mobile terminals

    DEFF Research Database (Denmark)

    Ojaroudiparchin, Naser; Shen, Ming; Pedersen, Gert F.

    2015-01-01

    This manuscript proposes a new design of phased array antenna for future fifth generation (5G) cellular communications. The proposed phased array antenna is designed on a low-cost N9000 PTFE substrate with overall size of 60×120×0.8 mm3. It consists of eight 28-GHz Vivaldi antenna elements used to...... characteristics in the entire operation band, which makes it suitable for millimeter-wave 5G communications. In addition, the performance of the antenna in the vicinity of user’s hand has been investigated in this study....

  15. Miniaturized Meander Slot Antenna Tor RFID TAG with Dielectric Resonator at 60 Ghz

    Directory of Open Access Journals (Sweden)

    JMAL Sabri

    2016-04-01

    Full Text Available Day after day, recent advances in millimeter wave communications have called for the development of compact and efficient antennas. Furthermore, the greatest challenges in this area is to get a good performance and a miniaturized antenna. In addition, the design of antenna, in the Silicon technology, is one of the key challenges. In this way, this work will focus on the design of the free 60 GHz band, high gain and high efficiency on-chip antenna meandering slots for transponder Radio Frequency Identification (RFID. Further, the stacked dielectric resonators (DRS will be arranged above the power element of on-chip antenna with an excitation of coplanar waveguide (CPW. We will use the Scattering Bond-Graph formalism like a new technique to design these proposed antennas and we will use the microwave Studio CST software simulation to validate the results. We have miniaturized the proposed antenna after having such a number of iteration and by applying the Bond Graph methodology, and the size of the antenna is about 1.2 * 1.1 mm2.

  16. A Broadband UHF Tag Antenna For Near-Field and Far-Field RFID Communications

    Directory of Open Access Journals (Sweden)

    M. Dhaouadi

    2014-12-01

    Full Text Available The paper deals with the design of passive broadband tag antenna for Ultra-High Frequency (UHF band. The antenna is intended for both near and far fields Radio Frequency Identification (RFID applications. The meander dipole tag antenna geometry modification is designed for frequency bandwidth increasing. The measured bandwidth of the proposed broadband Tag antenna is more than 140 MHz (820–960 MHz, which can cover the entire UHF RFID band. A comparison between chip impedance of datasheet and the measured chip impedance has been used in our simulations. The proposed progressive meandered antenna structure, with an overall size of 77 mm × 14 mm × 0.787 mm, produces strong and uniform magnetic field distribution in the near-field zone. The antenna impedance is matched to common UHF chips in market simply by tuning its capacitive and inductive values since a perfect matching is required in the antenna design in order to enhance the near and the far field communications. Measurements confirm that the designed antenna exhibits good performance of Tag identification for both near-field and far-field UHF RFID applications.

  17. Radiation and scattering from cylindrically conformal printed antennas. Ph.D. Thesis Final Report

    Science.gov (United States)

    Kempel, Leo C.; Volakis, John L.

    1994-01-01

    Microstrip patch antennas offer considerable advantages in terms of weight, aerodynamic drag, cost, flexibility, and observables over more conventional protruding antennas. These flat patch antennas were first proposed over thirty years ago by Deschamps in the United States and Gutton and Baisinot in France. Such antennas have been analyzed and developed for planar as well as curved platforms. However, the methods used in these designs employ gross approximations, suffer from extreme computational burden, or require expensive physical experiments. The goal of this thesis is to develop accurate and efficient numerical modeling techniques which represent actual antenna structures mounted on curved surfaces with a high degree of fidelity. In this thesis, the finite element method is extended to cavity-backed conformal antenna arrays embedded in a circular, metallic, infinite cylinder. Both the boundary integral and absorbing boundary mesh closure conditions will be used for terminating the mesh. These two approaches will be contrasted and used to study the scattering and radiation behavior of several useful antenna configurations. An important feature of this study will be to examine the effect of curvature and cavity size on the scattering and radiation properties of wraparound conformal antenna arrays.

  18. High Gain and High Directive of Antenna Arrays Utilizing Dielectric Layer on Bismuth Titanate Ceramics

    Directory of Open Access Journals (Sweden)

    F. H. Wee

    2012-01-01

    Full Text Available A high gain and high directive microstrip patch array antenna formed from dielectric layer stacked on bismuth titanate (BiT ceramics have been investigated, fabricated, and measured. The antennas are designed and constructed with a combination of two-, four-, and six-BiT elements in an array form application on microwave substrate. For gain and directivity enhancement, a layer of dielectric was stacked on the BiT antenna array. We measured the gain and directivity of BiT array antennas with and without the dielectric layer and found that the gain of BiT array antenna with the dielectric layer was enhanced by about 1.4 dBi of directivity and 1.3 dB of gain over the one without the dielectric layer at 2.3 GHz. The impedance bandwidth of the BiT array antenna both with and without the dielectric layer is about 500 MHz and 350 MHz, respectively, which is suitable for the application of the WiMAX 2.3 GHz system. The utilization of BiT ceramics that covers about 90% of antenna led to high radiation efficiency, and small-size antennas were produced. In order to validate the proposed design, theoretical and measured results are provided and discussed.

  19. A Compact Dual-Band RFID Tag Antenna Mountable on Metallic Objects

    Directory of Open Access Journals (Sweden)

    Byeonggwi Mun

    2015-01-01

    Full Text Available A compact (50 × 50 × 4 mm3 dual-band radio frequency identification (RFID tag antenna mountable on metallic objects is proposed for the ultra-high frequency (UHF band (917∼923.5 MHz and the microwave (MW band (2.4∼2.45 GHz. With the proximity-coupled feed loop, the proposed antenna consists of two symmetric planar inverted-F antenna (PIFA elements for the UHF band passive tag and a meander microstrip patch antenna for the MW band active tag. The performance of the proposed antenna is verified by mounting it on the different sizes of the metallic object. Furthermore, the passive tag antenna in the UHF band furthermore may be used for energy harvesting techniques to improve the lifetime of the active tag in the MW band. The measured maximum read range is 5.50 m in the UHF band and 14.15 m in the MW band when the proposed tag antenna is mounted on the metallic objects. The total efficiency for all operating frequency bands is higher than 50%. High isolation (>12 dB between tag antennas in the UHF band and the MW band is achieved.

  20. Efficient Design of the Microstrip Reflectarray Antenna by Optimizing the Reflection Phase Curve

    Directory of Open Access Journals (Sweden)

    Xing Chen

    2016-01-01

    Full Text Available The microstrip reflectarray antenna is an attractive directional antenna combining advantages of both the reflector and the microstrip array antenna. For the design of this kind of antenna, the conventional method, which is based on the reflection phase curve, may not be effective because of the approximations made in the design procedure. The common optimization method that employs an optimization algorithm in conjunction with the full-wave simulation to optimize the antennas’ structural parameters is able to achieve better performances in comparison with the conventional method; but it is impractical for large-scale microstrip reflectarray antennas due to too many structural parameters from variable reflection elements. To tackle the design problem of the microstrip reflectarray antenna, a new method is proposed for the first time. It optimizes the reflection phase curve rather than the structural parameters and then utilizes the optimized reflection phase curve to design the antenna. A microstrip reflectarray antenna working at 5.8 GHz and with a fixed size of 300 mm × 300 mm is designed for high gain as a sample design. The results show that the proposed method has greatly improved the antenna’s gain over 2.2 dB (from 19.7 dBi to 21.9 dBi in comparison with the conventional design method, and it only needs to optimize 6 structural parameters, in contrast to 22 for the common optimization method.

  1. COMPACT DUAL-BAND INVERTED L SHAPED MONOPOLE ANTENNA FOR WLAN APPLICATIONS

    Directory of Open Access Journals (Sweden)

    K Sumathi

    2015-12-01

    Full Text Available A highly compact and an optimized design of an Inverted L shaped printed monopole antenna with a simple compact ground plane is proposed. To make the designed antenna suitable for implantation it is embedded in FR-4 substrate and is presented. The antenna is designed for dual-band operation at 2.4GHz and 5.2GHz. It is suitable for Wireless Local Area Network (WLAN applications with return loss (S11 < -10dB. The antenna has two different resonant current paths that support two resonances at 2.44GHz and 5.18GHz (forming an F-shaped structure. The size of the antenna is 32.5mm × 19.6mm × 1.6mm. The antenna design is simulated using the tool Advanced Design System (ADS 2014. This antenna design has good return loss and radiation characteristics in both the required frequency bands. The radiation pattern obtained from the proposed antenna is an Omni directional radiation pattern in the E and H plane over the frequency ranges 2.4GHz and 5.2GHz.

  2. Instrumentation in Developing Chlorophyll Fluorescence Biosensing: A Review

    OpenAIRE

    Millan-Almaraz, Jesus R.; Guevara-Gonzalez, Ramon G.; Irineo Torres-Pacheco; Romero-Troncoso, Rene J.; Contreras-Medina, Luis M.; Carlos Duarte-Galvan; Fernandez-Jaramillo, Arturo A.

    2012-01-01

    Chlorophyll fluorescence can be defined as the red and far-red light emitted by photosynthetic tissue when it is excited by a light source. This is an important phenomenon which permits investigators to obtain important information about the state of health of a photosynthetic sample. This article reviews the current state of the art knowledge regarding the design of new chlorophyll fluorescence sensing systems, providing appropriate information about processes, instrumentation and electronic...

  3. Quantification of plant chlorophyll content using Google Glass.

    Science.gov (United States)

    Cortazar, Bingen; Koydemir, Hatice Ceylan; Tseng, Derek; Feng, Steve; Ozcan, Aydogan

    2015-04-01

    Measuring plant chlorophyll concentration is a well-known and commonly used method in agriculture and environmental applications for monitoring plant health, which also correlates with many other plant parameters including, e.g., carotenoids, nitrogen, maximum green fluorescence, etc. Direct chlorophyll measurement using chemical extraction is destructive, complex and time-consuming, which has led to the development of mobile optical readers, providing non-destructive but at the same time relatively expensive tools for evaluation of plant chlorophyll levels. Here we demonstrate accurate measurement of chlorophyll concentration in plant leaves using Google Glass and a custom-developed software application together with a cost-effective leaf holder and multi-spectral illuminator device. Two images, taken using Google Glass, of a leaf placed in our portable illuminator device under red and white (i.e., broadband) light-emitting-diode (LED) illumination are uploaded to our servers for remote digital processing and chlorophyll quantification, with results returned to the user in less than 10 seconds. Intensity measurements extracted from the uploaded images are mapped against gold-standard colorimetric measurements made through a commercially available reader to generate calibration curves for plant leaf chlorophyll concentration. Using five plant species to calibrate our system, we demonstrate that our approach can accurately and rapidly estimate chlorophyll concentration of fifteen different plant species under both indoor and outdoor lighting conditions. This Google Glass based chlorophyll measurement platform can display the results in spatiotemporal and tabular forms and would be highly useful for monitoring of plant health in environmental and agriculture related applications, including e.g., urban plant monitoring, indirect measurements of the effects of climate change, and as an early indicator for water, soil, and air quality degradation. PMID:25669673

  4. Quantification of Plant Chlorophyll Content Using Google Glass

    OpenAIRE

    Cortazar, Bingen; Koydemir, Hatice Ceylan; Tseng, Derek; Feng, Steve; Ozcan, Aydogan

    2015-01-01

    Measuring plant chlorophyll concentration is a well-known and commonly used method in agriculture and environmental applications for monitoring plant health, which also correlates with many other plant parameters including, e.g., carotenoids, nitrogen, maximum green fluorescence, etc. Direct chlorophyll measurement using chemical extraction is destructive, complex and time-consuming, which has led to the development of mobile optical readers, providing non-destructive but at the same time rel...

  5. Excitation energy transfer in natural photosynthetic complexes and chlorophyll trefoils: hole-burning and single complex/trefoil spectroscopic studies

    Energy Technology Data Exchange (ETDEWEB)

    Ryszard Jankowiak, Kansas State University, Department of Chemistry, CBC Bldg., Manhattan KS, 66505; Phone: (785) 532-6785

    2012-09-12

    In this project we studied both natural photosynthetic antenna complexes and various artificial systems (e.g. chlorophyll (Chl) trefoils) using high resolution hole-burning (HB) spectroscopy and excitonic calculations. Results obtained provided more insight into the electronic (excitonic) structure, inhomogeneity, electron-phonon coupling strength, vibrational frequencies, and excitation energy (or electron) transfer (EET) processes in several antennas and reaction centers. For example, our recent work provided important constraints and parameters for more advanced excitonic calculations of CP43, CP47, and PSII core complexes. Improved theoretical description of HB spectra for various model systems offers new insight into the excitonic structure and composition of low-energy absorption traps in very several antenna protein complexes and reaction centers. We anticipate that better understanding of HB spectra obtained for various photosynthetic complexes and their simultaneous fits with other optical spectra (i.e. absorption, emission, and circular dichroism spectra) provides more insight into the underlying electronic structures of these important biological systems. Our recent progress provides a necessary framework for probing the electronic structure of these systems via Hole Burning Spectroscopy. For example, we have shown that the theoretical description of non-resonant holes is more restrictive (in terms of possible site energies) than those of absorption and emission spectra. We have demonstrated that simultaneous description of linear optical spectra along with HB spectra provides more realistic site energies. We have also developed new algorithms to describe both nonresonant and resonant hole-burn spectra using more advanced Redfield theory. Simultaneous description of various optical spectra for complex biological system, e.g. artificial antenna systems, FMO protein complexes, water soluble protein complexes, and various mutants of reaction centers

  6. Design, development and microwave inter-comparison of dual slot antenna configurations for localized hepatic tumor management.

    Science.gov (United States)

    Zafa, J; Zafa, T; Zafa, H; Sharif, F

    2015-12-01

    Slot antennas are generally preferred for localized liver cancer treatment modalities due to desired radiation characteristics. An iterative thermal/microwave numerical routine is used to analyze regular and miniature slot antenna configurations at 5.8 GHz. A thermal/microwave solver determines the specific absorption rate to malignant tissues as a pre- processing step to compute microwave solution in terms of propagation wave number, return loss and insertion loss. The regular and miniature dual slots antenna geometries were then developed to estimate the return loss characteristics against antennas slot lengths at a constant frequency of 5.8 GHz. Results reveal that the regular geometry has return loss less than -5 dB as compared to antenna configuration. Furthermore, 5.8 GHz antenna geometry provides physical size reduction up to 50 %, lower fabrication cost and is a better minimally invasive choice due to further packed thermal ablation spots. PMID:26467919

  7. Light-induced dissociation of antenna complexes in the symbionts of scleractinian corals correlates with sensitivity to coral bleaching

    Science.gov (United States)

    Hill, R.; Larkum, A. W. D.; Prášil, O.; Kramer, D. M.; Szabó, M.; Kumar, V.; Ralph, P. J.

    2012-12-01

    Elevated temperatures in combination with moderate to high irradiance are known to cause bleaching events in scleractinian corals, characterised by damage to photosystem II (PSII). Photoprotective mechanisms of the symbiont can reduce the excitation pressure impinging upon PSII. In the bleaching sensitive species, Acropora millepora and Pocillopora damicornis, high light alone induced photoprotection through the xanthophyll cycle, increased content of the antioxidant carotenoid, β-carotene, as well as the dissociation of the light-harvesting chlorophyll complexes. The evidence is compatible with either the membrane-bound chlorophyll a-chlorophyll c 2-peridinin-protein (acpPC) complex or the peripheral peridinin-chlorophyll-protein complex, or both, disconnecting from PSII under high light. The acpPC complex potentially showed a state transition response with redistribution towards photosystem I to reduce PSII over-excitation. This apparent acpPC dissociation/reassociation was promoted by the addition of the xanthophyll cycle inhibitor, dithiothreitol, under high irradiance. Exposure to thermal stress as well as high light promoted xanthophyll de-epoxidation and increased β-carotene content, although it did not influence light-harvesting chlorophyll complex (LHC) dissociation, indicating light, rather than temperature, controls LHC dissociation. Photoinhibition was avoided in the bleaching tolerant species, Pavona decussata, suggesting xanthophyll cycling along with LHC dissociation may have been sufficient to prevent photodamage to PSII. Symbionts of P. decussata also displayed the greatest detachment of antenna complexes, while the more thermally sensitive species, Pocillopora damicornis and A. millepora, showed less LHC dissociation, suggesting antenna movement influences bleaching susceptibility.

  8. A Novel Design of Circular Edge Bow-Tie Nano Antenna for Energy Harvesting

    Science.gov (United States)

    Haque, Ahasanul; Reza, Ahmed Wasif; Kumar, Narendra

    2015-11-01

    In this study, a novel nano antenna is designed in order to convert the high frequency solar energy, thermal energy or earth re-emitted sun's energy into electricity. The proposed antenna is gold printed on a SiO2 layer, designed as a circular edge bow-tie with a ground plane at the bottom of the substrate. The Lorentz-Drude model is used to analyze the behavior of gold at the infrared band of frequencies. The proposed antenna is designed by 3D-electromagnetic solver, and analyzed for optimization of metal thickness, gap size, and antenna's geometrical length. Simulations are conducted in order to investigate the behavior of the antenna illuminated by the circularly polarized plane wave. The numerical simulations are studied for improving the harvesting E-field of the antenna within 5 THz-40 THz frequency range. The proposed antenna offers multiple resonance frequency and better return loss within the frequency bands of 23.2 THz to 27 THz (bandwidth 3.8 THz) and 31 THz to 35.9 THz (bandwidth 4.9 THz). An output electric field of 0.656 V/µm is simulated at 25.3 THz. The best fitted gap size at the feed point is achieved as 50 nm with the substrate thickness of 1.2 µm.

  9. Design of a compact tuning fork-shaped notched ultrawideband antenna for wireless communication application.

    Science.gov (United States)

    Shakib, M N; Moghavvemi, M; Mahadi, W N L

    2014-01-01

    A new compact planar notched ultrawideband (UWB) antenna is designed for wireless communication application. The proposed antenna has a compact size of 0.182λ × 0.228λ × 0.018λ where λ is the wavelength of the lowest operating frequency. The antenna is comprised of rectangular radiating patch, ground plane, and an arc-shaped strip in between radiating patch and feed line. By introducing a new Tuning Fork-shaped notch in the radiating plane, a stopband is obtained. The antenna is tested and measured. The measured result indicated that fabricated antenna has achieved a wide bandwidth of 4.33-13.8 GHz (at -10 dB return loss) with a rejection frequency band of 5.28-6.97 GHz (WiMAX, WLAN, and C-band). The effects of the parameters of the antenna are discussed. The experiment results demonstrate that the proposed antenna can well meet the requirement for the UWB communication in spite of its compactness and small size. PMID:24723835

  10. The Effect of Boundary Support and Reflector Dimensions on Inflatable Parabolic Antenna Performance

    Science.gov (United States)

    Coleman, Michael J.; Baginski, Frank; Romanofsky, Robert R.

    2011-01-01

    For parabolic antennas with sufficient surface accuracy, more power can be radiated with a larger aperture size. This paper explores the performance of antennas of various size and reflector depth. The particular focus is on a large inflatable elastic antenna reflector that is supported about its perimeter by a set of elastic tendons and is subjected to a constant hydrostatic pressure. The surface accuracy of the antenna is measured by an RMS calculation, while the reflector phase error component of the efficiency is determined by computing the power density at boresight. In the analysis, the calculation of antenna efficiency is not based on the Ruze Equation. Hence, no assumption regarding the distribution of the reflector surface distortions is presumed. The reflector surface is modeled as an isotropic elastic membrane using a linear stress-strain constitutive relation. Three types of antenna reflector construction are considered: one molded to an ideal parabolic form and two different flat panel design patterns. The flat panel surfaces are constructed by seaming together panels in a manner that the desired parabolic shape is approximately attained after pressurization. Numerical solutions of the model problem are calculated under a variety of conditions in order to estimate the accuracy and efficiency of these antenna systems. In the case of the flat panel constructions, several different cutting patterns are analyzed in order to determine an optimal cutting strategy.

  11. Swept frequency measurements of microwave antennas in feline and canine brain

    International Nuclear Information System (INIS)

    Interstitial microwave hyperthermia may prove to be an important therapy for malignant brain tumors. For safety and efficiency, the size and number of intracranial microwave antennas needs to be limited. Low power swept frequency measurements of VSWR were carried out in the brains of anesthetized cats and dogs utilizing stereotactically placed monopole antennas. The coupling efficiency of antennas at any frequency was degraded (VSWR>2:1) if a length of antenna less than 2h was inserted or if a plastic catheter was utilized. Such measurements indicate that (h) can be shortened 25% from the resonant length without seriously degrading antenna performance. The total length can be halved if a catheter with a high dielectric is used. High power tests (2-10w) of short antennas at 915 MHz in a ceramic catheter (e = 10) at 45-500C produce thermal fields approximately 2 cm in diameter in normal brain. It should be possible to efficiently and safely heat human brain tumors of average size utilizing these antennas and catheters at 915 MHz

  12. A Codesigned Compact Dual-Band Filtering Antenna with PIN Loaded for WLAN Applications

    Directory of Open Access Journals (Sweden)

    Shanxiong Chen

    2014-01-01

    Full Text Available A codesigned compact dual-band filtering antenna incorporating a PIN diode for 2.45/5.2 GHz wireless local area network (WLAN applications is proposed in this paper. The integrated filtering antenna system consists of a simple monopole radiator, a microstrip dual-band band-pass filter, and a PIN diode. The performance of the filtering antenna is notably promoted by optimizing the impedance between the antenna and the band-pass filter, with good selectivity and out-of-band rejection. The design process follows the approach of the synthesis of band-pass filter. In addition, the PIN diode is incorporated in the filtering antenna for further size reduction, which also widens the coverage of the bandwidth by about 230% for 2.4 GHz WLAN. With the presence of small size and good filtering performances, the proposed filtering antenna is a good candidate for the wireless communication systems. Prototypes of the proposed filtering antenna incorporating a PIN diode are fabricated and measured. The measured results including return losses and radiation patterns are presented.

  13. Variability of the specific fluorescence of chlorophyll in the ocean. Part 2. Fluorometric method of chlorophyll a determination

    OpenAIRE

    Miros³awa Ostrowska; Dimitrii N. Matorin; Dariusz Ficek

    2000-01-01

    Two methods of determining the chlorophyll a concentration in the sea have been formulated on the basis of artificially induced fluorescence measured with the aid of submersible fluorometers. The method of statistical correlation is founded on the empirical relationship between fluorescence and chlorophyll concentration. The theoretical model of fluorescence described in Part 1 of this paper (see Ostrowska et al. 2000, this volume) provides the basis of the other method, the physical...

  14. Evaluation of nitrogen status and total chlorophyll in longkong (Aglaia dookkoo Griff. leaves under water stress using a chlorophyll meter

    Directory of Open Access Journals (Sweden)

    Sdoodee, S.

    2005-07-01

    Full Text Available A chlorophyll meter (SPAD-502 was used to assess nitrogen status and total chlorophyll in longkong leaves, leaves from twelve of 10-year-old trees grown in the experimental plot at Prince of Songkla University, Songkhla province. The relationship between SPAD-502 meter reading and nitrogen status and total chlorophyll content analyzed in the laboratory was evaluated during 8 months (May-December 2003. It was found that the trend of the relationships in each month was similar. There was no significant differenceamong regression linears of all months. The data of 8 months showed that SPAD-reading and nitrogen content, and SPAD-reading and total chlorophyll content were related in a positive manner. They were Y = 0.19X+10.10, r = 0.76** (n = 240, and Y = 0.43X-7.89, r = 0.79** (n = 400, respectively. The SPAD-502 was then used to assess total nitrogen and total chlorophyll content during imposed water stress. Fifteen 4-yearold plants were grown in pots (each pot containing 50 kg soil volume. The experiment was arranged in acompletely randomized design with 3 treatments: (1 daily watering (2 once watering on day 7 (3 no watering with 5 replications during 14 days of the experimental period. Measurements showed a continuous decrease of SPAD-reading in the treatment of no watering. On day 14, a significant difference of SPAD- reading values between the treatment of daily watering and no watering was found. Then, the values of nitrogen content and total chlorophyll were assessed by using the linear regression equations. From the result, it is suggested that the measurement by chlorophyll meter is a rapid technique for the evaluation of total chlorophyll and nitrogen status in longkong leaves during water stress.

  15. Wrap-rib antenna concept development overview

    Science.gov (United States)

    Woods, A. A., Jr.; Garcia, N. F.

    1983-01-01

    The wrap rib antenna design of a parabolic reflector large space antenna is discussed. Cost estimates, design/mission compatibility, deployment sequence, ground based tests, and fabrication are discussed.

  16. High-temperature superconductor antenna investigations

    International Nuclear Information System (INIS)

    In this paper the use of superconductors to increase antenna radiation efficiency and gain is examined. Although the gain of all normal-metal antennas can be increased through the use of superconductors, some structures have greater potential for practical improvement than others. Some structures suffer a great degradation in bandwidth when replaced with superconductors, while for others the improvement in efficiency is trivial due to the minimal contribution of the conductor loss mechanism to the total losses, or the already high efficiency of the structure. The following antennas and related structures are discussed: electrically small antennas, impedance matching of antennas, microstrip antennas, microwave and millimeter-wave antenna arrays, and superdirective arrays. The greatest potential practical improvements occur for large microwave and millimeter-wave arrays and the impedance matching of antennas

  17. Microwave Antenna With Reduced Noise Leakage

    Science.gov (United States)

    Cha, A. G.

    1986-01-01

    Gain or gain-to-temperature ratio of dual-shaped subreflector receiving antenna increased when illumination is tapered near aperture edge. Taper imposed in antenna feed reduces spillover in transmitting mode and reduces noise pickup in receiving mode.

  18. Integrated resonant tunneling diode based antenna

    Energy Technology Data Exchange (ETDEWEB)

    Hietala, Vincent M. (Placitas, NM); Tiggers, Chris P. (Albuquerque, NM); Plut, Thomas A. (Albuquerque, NM)

    2000-01-01

    An antenna comprising a plurality of negative resistance devices and a method for making same comprising employing a removable standoff layer to form the gap between the microstrip antenna metal and the bottom contact layer.

  19. VLBI Antenna Calibration via GPS Project

    Data.gov (United States)

    National Aeronautics and Space Administration — We propose to investigate and develop an inexpensive system to determine: 1)VLBI antenna properties such as axis-offset, non-intersection of axis and antenna...

  20. Wireless Sensor Network Security Enhancement Using Directional Antennas: State of the Art and Research Challenges.

    Science.gov (United States)

    Curiac, Daniel-Ioan

    2016-01-01

    Being often deployed in remote or hostile environments, wireless sensor networks are vulnerable to various types of security attacks. A possible solution to reduce the security risks is to use directional antennas instead of omnidirectional ones or in conjunction with them. Due to their increased complexity, higher costs and larger sizes, directional antennas are not traditionally used in wireless sensor networks, but recent technology trends may support this method. This paper surveys existing state of the art approaches in the field, offering a broad perspective of the future use of directional antennas in mitigating security risks, together with new challenges and open research issues. PMID:27070601

  1. Characterization of Antennas on Dielectric and Magnetic Substrates Effective Medium Approximation

    Directory of Open Access Journals (Sweden)

    A. Sharaiha

    2009-12-01

    Full Text Available This paper presents a study of the effective medium approximation of a monopole antenna printed on either a dielectric or a magnetic substrate. Simple analytical formulas to determine the effective permeability of such an antenna have been proposed and validated. For this type of antenna as μr increases, the effective permeability will reach the value of 2 (maximum whereas, with the dielectric substrate, the effective permittivity continues to rise when increasing εr. This shows that, for very high permeability values, we will always have a size reduction below 30%.

  2. A Dual-polarized Microstrip Subarray Antenna for an Inflatable L-band Synthetic Aperture Radar

    Science.gov (United States)

    Zawadzki, Mark; Huang, John

    1999-01-01

    Inflatable technology has been identified as a potential solution to the problem of achieving small mass, high packaging efficiency, and reliable deployment for future NASA spaceborne synthetic aperture radar (SAR) antennas. Presently, there exists a requirement for a dual-polarized L-band SAR antenna with an aperture size of 10m x 3m, a center frequency of 1.25GHz, a bandwidth of 80MHz, electronic beam scanning, and a mass of less than 100kg. The work presented below is part of the ongoing effort to develop such an inflatable antenna array.

  3. Biologically inspired coupled antenna beampattern design

    Energy Technology Data Exchange (ETDEWEB)

    Akcakaya, Murat; Nehorai, Arye, E-mail: makcak2@ese.wustl.ed, E-mail: nehorai@ese.wustl.ed [Department of Electrical and Systems Engineering, Washington University in St Louis, St Louis, MO 63130 (United States)

    2010-12-15

    We propose to design a small-size transmission-coupled antenna array, and corresponding radiation pattern, having high performance inspired by the female Ormia ochracea's coupled ears. For reproduction purposes, the female Ormia is able to locate male crickets' call accurately despite the small distance between its ears compared with the incoming wavelength. This phenomenon has been explained by the mechanical coupling between the Ormia's ears, which has been modeled by a pair of differential equations. In this paper, we first solve these differential equations governing the Ormia ochracea's ear response, and convert the response to the pre-specified radio frequencies. We then apply the converted response of the biological coupling in the array factor of a uniform linear array composed of finite-length dipole antennas, and also include the undesired electromagnetic coupling due to the proximity of the elements. Moreover, we propose an algorithm to optimally choose the biologically inspired coupling for maximum array performance. In our numerical examples, we compute the radiation intensity of the designed system for binomial and uniform ordinary end-fire arrays, and demonstrate the improvement in the half-power beamwidth, sidelobe suppression and directivity of the radiation pattern due to the biologically inspired coupling.

  4. Antenna coupled photonic wire lasers.

    Science.gov (United States)

    Kao, Tsung-Yu; Cai, Xiaowei; Lee, Alan W M; Reno, John L; Hu, Qing

    2015-06-29

    Slope efficiency (SE) is an important performance metric for lasers. In conventional semiconductor lasers, SE can be optimized by careful designs of the facet (or the modulation for DFB lasers) dimension and surface. However, photonic wire lasers intrinsically suffer low SE due to their deep sub-wavelength emitting facets. Inspired by microwave engineering techniques, we show a novel method to extract power from wire lasers using monolithically integrated antennas. These integrated antennas significantly increase the effective radiation area, and consequently enhance the power extraction efficiency. When applied to wire lasers at THz frequency, we achieved the highest single-side slope efficiency (~450 mW/A) in pulsed mode for DFB lasers at 4 THz and a ~4x increase in output power at 3 THz compared with a similar structure without antennas. This work demonstrates the versatility of incorporating microwave engineering techniques into laser designs, enabling significant performance enhancements. PMID:26191717

  5. Compact Low Frequency Radio Antenna

    Science.gov (United States)

    Punnoose, Ratish J.

    2008-11-11

    An antenna is disclosed that comprises a pair of conductive, orthogonal arches and a pair of conductive annular sector plates, wherein adjacent legs of each arch are fastened to one of the annular sector plates and the opposite adjacent pair of legs is fastened to the remaining annular sector plate. The entire antenna structure is spaced apart from a conductive ground plane by a thin dielectric medium. The antenna is driven by a feed conduit passing through the conductive ground plane and dielectric medium and attached to one of the annular sector plates, wherein the two orthogonal arched act as a pair of crossed dipole elements. This arrangement of elements provides a radiation pattern that is largely omni-directional above the horizon.

  6. The radiation pattern of a monopole antenna attached to a conducting box

    Science.gov (United States)

    Chu, Andrew W. C.; Long, Stuart A.; Wilton, Donald R.

    1990-01-01

    A system investigation was undertaken to determine the radiation patterns of a monopole antenna mounted on a cubical conducting box over a ground plane. The effects of the location of the monopole and the electrical size of the box were compared with similar patterns measured over a flat ground plane and with numerically predicted values obtained from a method-of-moments patch code. It was concluded that the location at which a monopole antenna is mounted on a conducting box and the electrical size of the box clearly affect the overall radiation pattern of a monopole antenna. In general, mounting the antenna away from the center of the box will increase the depth of the nulls. In particular, planes will also increase the maximum E(phi) component of the field to the extent that it can become comparable to E(theta).

  7. HPLC Analysis of Chlorophyll a, Chlorophyll b, and Beta-Carotene in Collard Greens: A Project for a Problem-Oriented Laboratory Course.

    Science.gov (United States)

    Silveira, Augustine, Jr.; And Others

    1984-01-01

    High performance liquid chromatography (HPLC) is used to separate and quantitate beta-carotene, chlorophyll a, and chlorophyll b originating from collard greens. Experimental procedures used and typical results obtained are discussed. (JN)

  8. Ultra-wideband RF helmet antenna

    OpenAIRE

    Lebaric, Jovan; Tan, Ah-Tuan

    2000-01-01

    This paper addresses the development of an ultra-wideband, vertically polarized communications antenna integrated into the camouflage cover of a standard military-issue Kevlar helmet. The Helmet Camouflage Cover Antenna (referred to as the “helmet antenna’y is one of three antennas based on the antenna COMbat Wear INtegration (COMWIN) concept developed at the Naval Postgraduate School (NPS) for the man -portable implementation of the new Joint Tactical Radio System (JTRS). The results of c...

  9. Computer Simulation of a Plasma Vibrator Antenna

    OpenAIRE

    Nikolay N. Bogachev; Irina L. Bogdankevich; Namik G. Gusein-zade; Vladimir P. Tarakanov

    2013-01-01

    The use of new plasma technologies in antenna technology is widely discussed nowadays. The plasma antenna must receive and transmit signals in the frequency range of a transceiver. Many experiments have been carried out with plasma antennas to transmit and receive signals. Due to lack of experimental data and because experiments are difficult to carry out, there is a need for computer (numerical) modeling to calculate the parameters and characteristics of antennas, and to verify the parameter...

  10. Circularly polarized open-loop antenna

    OpenAIRE

    Li, Rong-Lin; Fusco, Vincent F.; Nakano, Hisamatsu

    2003-01-01

    A printed circular open-loop antenna is introduced as a simple structure for producing circular polarization; the antenna is fed with a coaxial probe. By introducing a gap within the circular loop a traveling-wave current is excited and thus circularly polarized radiation can be achieved. An optimized circularly polarized antenna is designed through numerical analysis using a so-called parametric method of moment technique. Experimental verification of the new antenna is presented. The antenn...

  11. Rectangular dielectric resonator antennas theory and design

    CERN Document Server

    Yaduvanshi, Rajveer S

    2016-01-01

    This book covers resonating modes inside device and gives insights into antenna design, impedance and radiation patterns. It discusses how higher-order modes generation and control impact bandwidth and antenna gain. The text covers new approaches in antenna design by investigation hybrid modes, H_Z and E_Z fields available simultaneously, and analysis and modelling on modes with practical applications in antenna design. The book will be prove useful to students, researchers and professionals alike.

  12. Phase shift measurements for antenna systems

    OpenAIRE

    Ogorodnijchuk, L. D.

    1999-01-01

    The necessity to create the high accurate antenna systems for radio systems and complexes [1] requires to provide this sphere of science and engineering with a high accurate phase-metering equipment. It's used to measure phase characteristics of units and blocks of antenna feeding systems, feeds, and antenna in the full sense [1-3], and to receive signals (phase radio direction finders, monopulse radars), and to control the operation (phase antenna arrays) as well. Also it's used for periodic...

  13. Knowledge-based antenna pattern extrapolation

    OpenAIRE

    Robinson, Michael

    2012-01-01

    We describe a theoretically-motivated algorithm for extrapolation of antenna radiation patterns from a small number of measurements. This algorithm exploits constraints on the antenna's underlying design to avoid ambiguities, but is sufficiently general to address many different antenna types. A theoretical basis for the robustness of this algorithm is developed, and its performance is verified in simulation using a number of popular antenna designs.

  14. Research of Klopfenstein taper UWB monopole antenna

    OpenAIRE

    Wang, Nan-Nan; Qiu, Jinghui; Zhang, Zhi-Feng; Zong, Hua; Ling-Ling, Zhong; Wei-Bo, Deng

    2011-01-01

    The tapered line theory in circuit can be applied to the design of the special-shaped monopole antenna in order to obtain better electrical characteristics. So a novel Klopfenstein taper monopole antenna is proposed. The impedance matching characteristic of the Klopfenstein tapered line is the best, and the Klopfenstein taper monopole antenna is designed based on it. On this basis, the coplanar waveguide-fed planar Klopfenstein taper monopole antennas are designed. The simulation and measurem...

  15. A novel coaxial CTS antenna design

    OpenAIRE

    Qiu, Jinghui; Xing, Xiaohang; Ling-Ling, Zhong

    2007-01-01

    CTS (Continuous Transverse Stub) antenna radiates electromagnetic wave with its transverse stubs on transmission line, and its pattern in horizon plane is omnidirectional. This paper proposes a novel coaxial CTS structure, in which a monopole is applied in coaxial CTS antenna, instead of a matching load. This method may not only improve the radiation ratio, but also reduce the height of antenna. There are two stubs and a monopole composing an antenna, and the dielectric in stubs is air, which...

  16. Nested-cone transformer antenna

    Science.gov (United States)

    Ekdahl, Carl A.

    1991-01-01

    A plurality of conical transmission lines are concentrically nested to form n output antenna for pulsed-power, radio-frequency, and microwave sources. The diverging conical conductors enable a high power input density across a bulk dielectric to be reduced below a breakdown power density at the antenna interface with the transmitting medium. The plurality of cones maintain a spacing between conductors which minimizes the generation of high order modes between the conductors. Further, the power input feeds are isolated at the input while enabling the output electromagnetic waves to add at the transmission interface. Thus, very large power signals from a pulse rf, or microwave source can be radiated.

  17. Broadband antenna arrays using planar horns

    OpenAIRE

    Braude, V. B.; Sukhovetskaya, S. B.

    1997-01-01

    Broadband antennas are vitally important for various applications ranging from TV broadcasting to carrier-free ground-probing radars. We propose a microwave broadband antenna array (BAA), which may be realised using microstrip planar horns — flared end-fire radiating slot lines, known as Vivaldi-type antennas.

  18. Compact Dual-Mode Microwave Antenna

    Science.gov (United States)

    Carr, K. L.

    1982-01-01

    Compact dual-mode antenna, 3.66 cm wide by 1.83 cm thick is used both for heating and thermographic detection of tumors in cancer research. Temperature sensor operates independently or simultaneously with heater. Antenna includes 1.6-GHz transmitter and 4.76-GHz receiver. Strip heater between antennas controls temperature of device. Maximum power output is 25 W.

  19. Isolation between three antennas at 700 MHz

    DEFF Research Database (Denmark)

    Bahramzy, Pevand; Svendsen, Simon; Pedersen, Gert F.

    2015-01-01

    To address the antenna design challenges posed by many frequency bands, introduced with long-term evolution deployment, this study proposes the use of separate transmit (Tx) and receive (Rx) narrow-band antennas. In addition, a diversity Rx (Dx) antenna is needed for multiple-input multiple-output...

  20. 47 CFR 80.967 - Antenna system.

    Science.gov (United States)

    2010-10-01

    ... 47 Telecommunication 5 2010-10-01 2010-10-01 false Antenna system. 80.967 Section 80.967... MARITIME SERVICES Radiotelephone Installation Required for Vessels on the Great Lakes § 80.967 Antenna system. The antenna must be omni-directional, vertically polarized and located as high as practicable...