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Antenna Size (antenna + size)
Selected AbstractsDifferential expression of antenna and core genes in Prochlorococcus PCC 9511 (Oxyphotobacteria) grown under a modulated light,dark cycleENVIRONMENTAL MICROBIOLOGY, Issue 3 2001Laurence Garczarek The continuous changes in incident solar light occurring during the day oblige oxyphototrophs, such as the marine prokaryote Prochlorococcus, to modulate the synthesis and degradation rates of their photosynthetic components finely. How this natural phenomenon influences the diel expression of photosynthetic genes has never been studied in this ecologically important oxyphotobacterium. Here, the high light-adapted strain Prochlorococcus sp. PCC 9511 was grown in large-volume continuous culture under a modulated 12 h,12 h light,dark cycle mimicking the conditions found in the upper layer of equatorial oceans. The pcbA gene encoding the major light-harvesting complex showed strong diel variations in transcript levels with two maxima, one before the onset of illumination and the other near the end of the photoperiod. In contrast, the mRNA level of psbA (encoding the reaction centre II subunit D1), the monocistronic transcript of psbD (encoding D2) and the dicistronic transcript of psbDC were all tightly correlated with light irradiance, with a minimum at night and a maximum at noon. The occurrence of a second peak during the dark period for the monocistronic transcript of psbC (encoding one of the PS II core Chl a antenna proteins) suggested the involvement of post-transcriptional regulation. Differential expression of the external antenna and core genes may constitute a mechanism of regulation of the antenna size to cope with the excess photon fluxes that Prochlorococcus cells experience in the upper layer of oceans around midday. The 5, ends of all transcripts were mapped, and a conserved motif, 5,-TTGATGA-3,, was identified within the putative psbA and pcbA promoters. [source] A compact substrate integrated waveguide H-plane horn antenna with dielectric arc lensINTERNATIONAL JOURNAL OF RF AND MICROWAVE COMPUTER-AIDED ENGINEERING, Issue 5 2007Wenquan Che Abstract An H-plane horn antenna constructed into SIW (substrate integrated waveguide) is proposed. It has a dielectric arc lens for better directivity and a simple microstrip transition as feed. The horn, the lens and the transition share the same substrate. The resulting formula from optical principles shows that the suitable dielectric lens can improve the directivity of the antenna significantly. A prototype was fabricated; the antenna size is 39.175 × 14 × 2 mm3. The frequency band is from 25.5 to 28.5 GHz. The measured gain of this antenna is about 9 dB; the bandwidth, at 10 dB return loss, is over 12%. © 2007 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2007. [source] A novel miniature monopole tag antenna for passive UHF RFID applicationsMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 12 2010Hsien-Wen Liu Abstract A novel miniature monopole tag antenna for passive Ultra-High Frequency (UHF) radio frequency identification (RFID) operation is presented. The antenna possesses a two-sided structure that is printed on an FR4 substrate and fed by a 50-, microstrip line. By properly using helical strips and vias, the antenna size can be reduced to a small volume of 10 (L) × 9.5 (W) × 0.8 (H) mm3 to be easily integrated within various portable devices. A miniaturized quasi-lumped circuit is also designed to attain a good impedance matching between the antenna and the chip. Experimental results demonstrate that the antenna has a suitable operating band about 914,939 MHz and also quite omnidirectional radiation pattern with appreciable gain. Moreover, the proposed compact tag antenna, capable of achieving a maximum readable range of about 5.6 m with an EIRP equal to 4 W, is well suited for RFID applications. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52:2770,2772, 2010; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.25596 [source] Slits-loaded microstrip antennas for circular polarizationMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 9 2010N. Nasimuddin Abstract Novel diagonally slits-loaded compact microstrip antennas are proposed for circular polarization (CP). A group of four slits is loaded on the square patch radiator for compact antenna size with CP radiation. The slit with unequal sizes loaded on square patch in diagonal directions is used to achieve CP radiation. The combined V -shaped and square slits, diagonally loaded, microstrip antenna is compact when compared with V -shaped slits loaded microstrip antenna. The measured 10-dB return loss and 3-dB axial-ratio bandwidths are 3.55% and 0.82%, respectively, for a combined V -shaped and square slits loaded microstrip patch antenna. The overall size of the antenna is 0.256,0×0.256,0×0.0136,0 at 2.55 GHz. The proposed slits-loaded patch radiator is useful for compact circularly polarized microstrip antenna and array designs. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 2043,2049, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25417 [source] A size reduced CRLH resonant antenna based on interdigital capacitors with defected ground structureMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 9 2010M.-J. Lee Abstract A new composite right/left-handed (CRLH) resonant antenna with interdigital capacitors for a size reduction is proposed in this letter. This antenna consists of three sectional patches, two interdigital lines (capacitors) with a defected ground, and two shorting pins. A rectangular patch is split into three sections and each section is coupled with an interdigital line. When the proposed antenna is operated in the LH resonant mode, the antenna size is reduced by 33% and the antenna gain is increased by 7 dB as compared with one without defected ground structures. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 2142,2145, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25362 [source] Low-profile radio frequency identification tag antenna using a trapezoid patch mountable on metallic surfacesMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 8 2010Horng-Dean Chen Abstract A trapezoid patch antenna, designed for ultra high frequency band radio frequency identification tag mountable on metallic surfaces, is presented in this article. The proposed antenna has a simple and low-profile (0.8 mm thick) structure. The impedance matching can be easily achieved by adjusting the upper-side width and the height of the trapezoid patch. The reading range of the proposed antenna is verified by calculation and measurement, which shows good agreement. Varying antenna size can provide applicable reading range to suit different applications. The results obtained show that the proposed antenna can work efficiently in free space and on metallic objects. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 1697,1700, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25310 [source] Design of a planar ultra-wideband miniature monopole antenna for wireless USB dongle devicesMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 5 2010Yu-Chia Chang Abstract This article proposes a 3.1,5 GHz ultra-wideband antenna, defined by a ,10 dB return loss. The simplified planar antenna structures, compact size, and low profile make it profitable to the application of the embedded antenna in wireless universal serial bus dongle devices. The slit shape on the monopole radiator is tuned for miniature antenna size. A parasitic stub on the ground is adopted to increase antenna bandwidth for achieving 3.1,5 GHz impedance bandwidth. To reduce manufacturing cost and practical fabrication, we also propose a simplified rectangular antenna structure. It is found that wideband characteristics of the simplified rectangular structure antenna are similar to that of semicircular base structure. Finally, the antenna prototypes are fabricated and the antenna characteristics are measured. The radiation patterns are omnidirectional in azimuth cut. Moreover, the S -parameter of antenna characteristics has been measured. The consistency between the simulated results and the measurement results confirms the practicability of these techniques. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 1013,1016, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25121 [source] Ultra-wideband coplanar boat microstrip patch with modified ground plane by using electromagnetic band-gap structure for wireless communicationMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 5 2010Dalia N. Elsheakh Abstract A new antenna structure using triangular patch alongside a small trapezoidal shape ground plane with proximity fed is proposed in this article. The proposed antenna design provides a bandwidth in the range from 2 < 35 GHz with band discontinuities. Improvement is done in antenna performance by using electromagnetic band-gap (EBG) structure. First, dumb-bell shapes as 2D-EBG are etched in the feeding line. Second, embedded spiral artificial magnetic conductor with four arms to introduce sufficient inductive impedance is done. The resultant bandwidth increases to three times than the original bandwidth and reduces the antenna size as well as enhancing the antenna gain. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 1159,1164, 2010; Published online in Wiley InterScience (www.interscience. wiley.com). DOI 10.1002/mop.25129 [source] Internal wideband monopole antenna for MIMO access-point applications in the WLAN/WIMAX bandsMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 5 2008Jui-Hung Chou Abstract A three-antenna MIMO system capable of generating a wide operating bandwidth of 2400,5850 MHz for access-point applications is introduced. The proposed design is based on a bent metal-plate monopole antenna with a compact size of 20 × 20 × 14 mm3. The three antennas are equally spaced along the perimeter of a circular ground and all generate a wide bandwidth of larger than 4 GHz. With the antenna short-circuiting facing the center of the ground, not only the overall antenna size is reduced but also good isolation of less than ,20 dB can easily be obtained. Calculated envelope correlation is also less than 0.002 across the operating band. The design prototype of the antenna is discussed in detail in the article. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1146,1148, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23333 [source] CPW-FED shorted F-shaped monopole antenna for 5.8-GHz RFID applicationMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 3 2006Wen-Chung Liu Abstract A novel coplanar waveguide (CPW)-fed F-shaped planar monopole antenna obtained by embedding folded slots in a rectangular patch on a single-layer substrate is proposed. To expand the impedance bandwidth and miniaturize the antenna size for suitable use in 5.8-GHz radio frequency identification (RFID) systems, a branch of the F-shaped antenna is shorted. The designed antenna including ground plane is only 16.8 mm in height and 13 mm in width and can operate in the 5.8-GHz frequency band with measured impedance bandwidth and average antenna gain of 640 MHz and 4 dBi, respectively, as well as broadside radiation patterns. These properties make this antenna suitable for RFID tags. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 573,575 2006; Published online in Wiley InterScience (www.interscience.wiley.com) DOI 10.1002/mop.21410 [source] A slow-wave structure with Koch fractal slot loopsMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 2 2002Jung-Hyo Kim Abstract In this Letter, a Koch slot loop in the ground plane has been utilized to obtain slow-wave characteristics, and its electrical performances are analyzed with the use of the ABCD matrix approach. The validity of this approach has been verified through experimental results, and this technique was then applied to microstrip patch antennas in order to obtain a small antenna size. The cross-sectional areas of this type of antenna are 47% to 65% smaller than those of conventional square patches. © 2002 Wiley Periodicals, Inc. Microwave Opt Technol Lett 34: 87,88, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10381 [source] Variations in Photosystem I Properties in the Primordial Cyanobacterium Gloeobacter violaceus PCC 7421PHOTOCHEMISTRY & PHOTOBIOLOGY, Issue 1 2010Mamoru Mimuro We compared the optical properties of the trimeric photosystem (PS) I complexes of the primordial cyanobacterium Gloeobacter violaceus PCC 7421 with those of Synechocystis sp. PCC 6803. Gloeobacter violaceus PS I showed (1) a shorter difference maximum of P700 by approximately 2 nm, (2) a smaller antenna size by approximately 10 chlorophyll (Chl) a molecules and (3) an absence of Red Chls. The energy transfer kinetics in the antennae at physiological temperatures were very similar between the two species due to the thermal equilibrium within the antenna; however, they differed at 77 K where energy transfer to Red Chls was clearly observed in Synechocystis sp. PCC 6803. Taken together with the lower P700 redox potential in G. violaceus by approximately 60 mV, we discuss differences in the optical properties of the PS I complexes with respect to the amino acid sequences of core proteins and further to evolution of cyanobacteria. [source] CP43,, the isiA Gene Product, Functions as an Excitation Energy Dissipator in the Cyanobacterium Synechococcus sp.PHOTOCHEMISTRY & PHOTOBIOLOGY, Issue 3 2001PCC 794 ABSTRACT Under conditions of iron deficiency certain cyanobacteria induce a chlorophyll (Chl)-binding protein, CP43,, which is encoded by the isiA gene. We have previously suggested that CP43, functions as a nonradiative dissipator of light energy. To further substantiate its functional role an isiA overexpression construct was introduced into the genome of a cyanobacterium Synechococcus sp. PCC 7942 (giving isiAoe cells). The presence of functional CP43, in isiAoe cells was confirmed by Western blot as well as by the presence of a characteristic blueshift of the red Chl a absorption peak and a notable increase in the 77 K fluorescence peak at 685 nm. Compared to wild-type cells isiAoe cells, with induced CP43,, had both smaller functional antenna size and decreased yields of room temperature Chl fluorescence at various light irradiances. These observations strongly suggest that isiAoe cells, with induced CP43,, have an increased capacity for dissipating light energy as heat. In agreement with this hypothesis isiAoe cells were also more resistant to photoinhibition of photosynthesis than wild-type cells. Based on these results we have further strengthened the hypothesis that CP43, functions as a nonradiative dissipator of light energy, thus protecting photosystem II from excessive excitation under iron-deficient conditions. [source] Probe-fed microstrip antennas loaded with very high-permittivity ceramicsINTERNATIONAL JOURNAL OF RF AND MICROWAVE COMPUTER-AIDED ENGINEERING, Issue 5 2006Y. Hwang Abstract This article reports the feasibility study of miniaturizing probe-fed microstrip patch antennas by dielectric loading. The loading materials are barium tetratitanate ceramics of very high dielectric constant (,r = 38, 80). It is shown that, simply through loading, the antenna sizes are greatly reduced; however, the antenna performances are deteriorated. For instance, the antenna gain becomes lower. Then enhancement of the antenna performances follows. A substrate,superstrate structure is used to recover the gain. Both the experiments and the finite-difference time-domain (FDTD) simulations demonstrate that the gain and impedance bandwidth can be retrieved such that they are comparable to those of conventional microstrip antennas loaded with low permittivity materials (,r < 3). © 2006 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2006. [source] | |||||||||||||