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dBi
Selected AbstractsBeta-amyloid peptide stimulates endozepine release in cultured rat astrocytes through activation of N -formyl peptide receptorsGLIA, Issue 13 2008Tursonjan Tokay Abstract Astroglial cells synthesize and release endozepines, a family of neuropeptides derived from diazepam-binding inhibitor (DBI). The authors have recently shown that ,-amyloid peptide (A,) stimulates DBI gene expression and endozepine release. The purpose of this study was to determine the mechanism of action of A, in cultured rat astrocytes. A,25,35 and the N -formyl peptide receptor (FPR) agonist N -formyl-Met-Leu-Phe (fMLF) increased the secretion of endozepines in a dose-dependent manner with EC50 value of ,2 ,M. The stimulatory effects of A,25,35 and the FPR agonists fMLF and N -formyl-Met-Met-Met (fMMM) on endozepine release were abrogated by the FPR antagonist N - t -Boc-Phe-Leu-Phe-Leu-Phe. In contrast, A,25,35 increased DBI mRNA expression through a FPR-independent mechanism. A,25,35 induced a transient stimulation of cAMP formation and a sustained activation of polyphosphoinositide turnover. The stimulatory effect of A,25,35 on endozepine release was blocked by the adenylyl cyclase inhibitor somatostatin, the protein kinase A (PKA) inhibitor H89, the phospholipase C inhibitor U73122, the protein kinase C (PKC) inhibitor chelerythrine and the ATP binding cassette transporter blocker glyburide. Taken together, these data demonstrate for the first time that A,25,35 stimulates endozepine release from rat astrocytes through a FPR receptor positively coupled to PKA and PKC. © 2008 Wiley-Liss, Inc. [source] Single dose intravenous thioacetamide administration as a model of acute liver damage in ratsINTERNATIONAL JOURNAL OF EXPERIMENTAL PATHOLOGY, Issue 4 2008Tse-Min Chen Summary Thioacetamide (TAA) has been used extensively in the development of animal models of acute liver injury. Frequently, TAA is administered intraperitoneally to induce liver damage under anaesthesia. However, it is rarely administered by intravenous injection in conscious rats. The experiments in this study were designed to induce acute liver damage by single intravenous injection of TAA (0, 70 and 280 mg/kg) in unrestrained rats. Biochemical parameters and cytokines measured during the 60-h period following TAA administration, included white blood cells (WBC), haemoglobulin (Hb), platelet, aspartate transferase (GOT), alanine transferase (GPT), total bilirubin (TBIL), direct bilirubin (DBI), albumin, ammonia (NH3), r-glutamyl transpeptidase (r-GT), tumour necrosis factor-, (TNF-,) and interleukin-6 (IL-6). Rats were sacrificed by decapitation 60 h after TAA administration and livers were removed immediately for pathology and immunohistochemical (IHC) examination. Another group of rats were sacrificed by decapitation 1, 6 and 24 h after TAA administration and livers were removed immediately for time course change of pathology and IHC examination. TAA significantly increased blood WBC, GOT, GPT, TBIL, DBIL, NH3, r-GT, TNF-, and IL-6 levels but decreased the blood Hb, platelet and albumin level. The levels of histopathological damage in the liver after intravenous TAA administration were also increased with a dose-dependent trend and more increased at 60 h after TAA administration. The levels of inducible nitric oxide synthase (iNOS) and nuclear factor-,B (NF-,B) detected by IHC in the liver after intravenous TAA administration were also increased with a dose-dependent trend and more increased at 1 h after TAA administration. Single intravenous TAA administration without anaesthesia is a restorable animal model which may be used to investigate acute liver damage. [source] A Behavioral Genetic Analysis of the Relationship Between the Socialization Scale and Self-Reported DelinquencyJOURNAL OF PERSONALITY, Issue 1 2000Jeanette Taylor This investigation examined the genetic (A), and shared (C) and nonshared (E) environmental variance contributions to the relationship of self-reported delinquency (as measured by the "Delinquent Behavior Inventory" [DBI; Gibson, 1967]) to the Socialization (So) scale of the California Psychological Inventory using univariate and bivariate structural equation models. The scales were administered to 222 male (145 monozygotic; 77 dizygotic) and 159 female (107 monozygotic; 52 dizygotic) 16- to 18-year-old same-sex twin pairs. Principal components analysis with varimax rotation revealed three interpretable So factors representing family/home environment, self-concept, and behavioral control. Univariate modeling suggested sex differences in etiological influences associated with individual differences in most scales. The bivariate ACE model fit the data, suggesting that the covariance between the So scale and self-reported delinquency owes in part to shared etiological factors. [source] Effect of hydrogen-bonding interaction on radical polymerization of di- n -butyl itaconateJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 21 2003Tomohiro Hirano Radical polymerizations of di- n -butyl itaconate (DBI) were examined in the presence of amide compounds that could form a complex with DBI monomer via a hydrogen-bonding interaction. The use of amide compounds as solvents succeeded to suppress the intramolecular chain-transfer reaction significantly, whereas catalytic amounts of amide compounds were of little effect. It was also assumed that a hydrogen-bonding interaction plays an important role not only for suppression of the intramolecular chain-transfer reaction but for stereospecificity of polymerization. These results suggested that even a weak hydrogen-bonding interaction could be used for control of a radical polymerization reaction. [source] Change in sugar, sterol and fatty acid composition in banana meristems caused by sucrose-induced acclimation and its effects on cryopreservationPHYSIOLOGIA PLANTARUM, Issue 1 2006Guo-Yu Zhu To understand the mechanisms of sucrose-induced acclimation in relation to plant cryopreservation, sugars, sterols, fatty acids of different lipid fractions (neutral lipids, glycolipids and sphingolipids and phospholipids), as well as free fatty acids were analyzed in proliferating meristem cultures of different banana varieties. The four banana varieties that were selected show different post-thaw shoot regeneration rates (0,53.4%). All mentioned parameters were analyzed using (1) control meristems that were cultured on a normal sucrose concentration (0.09 M), which resulted in low survival after cryopreservation; and (2) 2-week sucrose precultured meristems (0.4 M). This sucrose preculture, essential for regeneration after cryopreservation, resulted in a significant increase of each of seven sugars detected. The ratio of stigmasterol/sitosterol (St/Si) in sucrose-pretreated meristems significantly increased. The sucrose pretreatment also resulted in a significant increase of total fatty acid content of the neutral lipid fraction and of the glycolipid and sphingolipid fraction, as well as the total free fatty acid content. The individual fatty acid content of the phospholipids was differently changed by the sucrose pretreatment for the given varieties studied. In most cases, sucrose pretreatment resulted in an increase of the double bond index (DBI) in the neutral lipids and a decrease of DBI in the glycolipids and sphingolipids, in phospholipids as well as in free fatty acids. Principal component analysis of all collected data revealed that (1) for the control material, sucrose and total sugar contents were closely linked to the post-thaw shoot regeneration, suggesting that sucrose and total sugar may be main limiting factors to survive cryopreservation; (2) accumulation of large quantities of sugars (glucose, fructose, sucrose and total sugar) in sucrose-pretreated material cannot explain the differences in survival after cryopreservation of the four banana varieties. We assume that a minimal amount of sugars is needed in meristem cultures to survive cryopreservation. Still, other limiting factors do influence the survival following the sucrose pretreatment. We observed that the parameters which are closely linked to the post-thaw shoot regeneration are a minimal change in the ratios of St/Si, the minimal change of the DBI of phospholipids and free fatty acids, as well as linoleic acid content (C18:2); and (3) inositol, raffinose, myristic acid (C14:0) and oleic acid (C18:1) were present in small quantities; however, they could be correlated to survival after cryopreservation, suggesting that they may be also involved in cryopreservation process. [source] Molecular cloning and expression profiles of the acyl-CoA-binding protein gene from the cotton bollworm Helicoverpa armigeraARCHIVES OF INSECT BIOCHEMISTRY AND PHYSIOLOGY (ELECTRONIC), Issue 2 2008Jia-Lin Wang Abstract Acyl-CoA-binding protein (ACBP), also known as the diazepam-binding inhibitor (DBI), has been identified in diverse species and is evolutionarily conserved in plants and animals. In a recent study, an ACBP cDNA (HaACBP) encoding 85 amino acids was isolated from the cotton bollworm Helicoverpa armigera. The isolated protein is highly homologous to the ACBP present in the Bombyx mori midgut, where it is highly expressed. Northern and Western blot analyses revealed that HaACBP is expressed predominantly in the midgut. Moreover, Northern blotting revealed that HaACBP was probably stimulated by a high juvenile hormone titer at ecdysis and increased along with feeding at 12 h post-ecdysis. Immunohistochemistry of the midgut revealed that HaACBP is localized in columnar cells. Data from the Northern blotting and immunohistochemistry suggested that HaACBP was expressed during the larval period and is probably responsible for nutrition absorption. However, Western blot analysis of the midgut at different developmental stages indicated that HaACBP was upregulated during larval molting and metamorphosis, which suggested that HaACBP expression was posttranscriptionally regulated. Arch. Insect Biochem. Physiol. 68:79,88, 2008. © 2008 Wiley-Liss, Inc. [source] Two-dimensional beam-scanning using tapered slot antennas and piezoelectric transducersINTERNATIONAL JOURNAL OF RF AND MICROWAVE COMPUTER-AIDED ENGINEERING, Issue 4 2006Sang-Gyu Kim Abstract A wideband phased array is demonstrated using antipodal exponentially-tapered slot-antenna (ATSA) arrays operated by piezoelectric transducer (PET)-controlled phase shifters. A 4 × 4 ATSA array is designed to scan two-dimensionally across the entire X -band. The phase shifters for 2D scanning consist of two sets of multiline phase shifters controlled by the PET for scanning in both planes. The 2D phased array has an antenna gain greater than 8 dBi, including all losses due to the phase shifters and transitions, and shows a wide beam-scanning capability greater than 30° in both the E -plane and the H -plane. © 2006 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2006. [source] Compact top-loaded ultra-wideband biconical antenna for indoor base-station applicationsMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 11 2010W. J. Lu Abstract A biconical antenna employing the top-loaded technique is proposed for ultra-band (UWB) operation. The antenna is composed of a small cone mounted on a top-loaded disc and a conical ground plane, with both cones electrically connected together using four shorting pins to reduce the lower cutoff frequency. The antenna is investigated using computer simulation and measurement. Results show that the antenna has an impedance bandwidth from 0.8 GHz to over 11.2 GHz, dipole-like omnidirectional radiation pattern, average gain of about 4.2 dBi, and average radiation efficiency of over 88%. The antenna has the advantageous features of compact size, low profile, simple structure, and ultra-wideband characteristic and so is suitable for indoor base-station applications of many existing and future wireless and UWB systems. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52:2594,2598, 2010; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.25540 [source] Compact high-gain printed loop-antenna array integrated into a 5-GHz WLAN access pointMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 10 2010Tzi-Chieh Hong Abstract A printed, planar loop-antenna array having a compact structure and high-gain, directional radiation properties for WLAN operation in the 5 GHz band is presented. The antenna-array design is composed of four-folded loops arranged to be of 2 × 2 configuration, printed on both sides of a 1.6-mm thick FR4 substrate, and one system printed circuit board (PCB) serving as an efficient reflector for the loops. The antenna array is set within the boundary of the PCB (size of 50 mm ×65 mm) and stacked there above by a separation distance of 5.4 mm only. That's, the design integrates the system PCB of an access point (AP) into an internal antenna solution for compact outdoor AP applications. The results show that good input matching with voltage standing wave ratio (VSWR) below 1.5 over the 5150,5825 MHz band can be achieved. Directional radiation patterns with peak gain at about 10 dBi were also obtained. Details of the antenna design are described and discussed. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52:2261,2267, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25487 [source] Efficient and high-gain aperture coupled superstrate antenna arrays for 60 GHz indoor communication systemsMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 10 2010Hamsakutty Vettikalladi Abstract Efficient and high-gain aperture coupled patch antenna arrays with superstrate at 60 GHz are studied and presented. It is noted that adding a superstrate with a specific size will induce a significant effect on antenna gain and radiation patterns. This capability is applied on the design of 2 × 2 and 4 × 4 arrays for high-gain application. The maximum measured gain of a 2 × 2 superstrate antenna array is 16 dBi with an efficiency of 63%, which is 4 dB higher than that of a classical 2 × 2 array at 60 GHz. The 2:1 measured voltage standing wave ratio (VSWR) bandwidth is 6.8%. Also the maximum gain measured for a 4 × 4 superstrate antenna array is found to be 19.7 dBi with an estimated efficiency of 51%. The radiation patterns are found to be broadside all over the frequency band with very low back radiation. Hence aperture coupled superstrate antenna array is a good candidate for high-efficient high-gain application at 60 GHz. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52:2352,2356, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25455 [source] A compact pentagonal monopole antenna for portable UWB systemsMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 10 2010Paulbert Thomas Abstract Design of a compact microstrip-fed ultra-wideband antenna suitable for USB dongle and other such space constraint applications is presented. The structure consists of a pentagonal monopole element and a modified ground plane that gives an impedance bandwidth from 2.8 to 12 GHz. Radiation patterns are stable and omni-directional throughout the band with an average gain of 2.84 dBi. The antenna occupies only 11 × 30 mm2 on FR4 substrate with permittivity 4.4. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52:2390,2393, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25449 [source] Adding microstrip line at the bottom of PCB for enhancing antenna bandwidthMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 9 2010B.-G. Cho Abstract In this article, added microstrip line at the bottom area of printed circuit board (PCB) is proposed for improving the bandwidth of GSM900, DCS1800, and PCS1900. By printing the microstrip line at the bottom area of PCB, frequency bandwidth of slim-type cellular phone which has a low-profile monopole antenna is improved. Dimension of the microstrip line is 45 mm × 9 mm. The width and length of the microstrip line is modified for good bandwidth. The measured return loss of the antenna is better than 7.3 dB for low and high band. Measured peak gains of the proposed antenna present 3.41, 5.48, and 5.95 dBi in each band, respectively. Details of the antenna design are described. Its performances are also presented. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 1984,1988, 2010; Published online in Wiley InterScience (www.interscience. wiley.com). DOI 10.1002/mop.25399 [source] A coaxial fed flower shaped multi-element suspended patch antenna with illumination area in the form of a ringMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 9 2010T.K. Chandra Shekhar Abstract A multi-element suspended microstrip patch antenna with flower shaped printed pattern excited at its centre by a coaxial feed is presented. All the radiating patch elements are electromagnetically coupled symmetrically to the same coaxial feed, thereby eliminating the need for a separate power division network. With three or more elements, the antenna beam illuminates an area in the form of a ring symmetric about the axis perpendicular to the plane of the patch elements. The antenna offers a gain in the range 5,6 dBi with a 3 dB beamwidth of about 50° in any cross-sectional plane passing through the vertical axis. Details of the simulation studies carried out on the antenna with one to five elements and experimental results on the fabricated antennas are presented. The antenna has potential applications in remote sensing and biomedical areas, particularly for microwave imaging. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 2037,2043, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25418 [source] A coupling-fed multiband antenna for WLAN/WiMAX applicationsMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 6 2010Shaoli Zuo Abstract A coupling-fed printed monopole antenna applied to wireless local area network/worldwide interoperability for microwave access (WLAN/WiMAX) applications is proposed. By using a pair of branch-shaped strips, which are symmetrical with a gradual changing strip, the proposed antenna exhibits multiband performance to meet the requirements of WLAN in the 2.4/5.2/5.8 GHz bands and WiMAX in the 2.5/3.5/5.5 GHz bands. The proposed antenna has good omnidirectional radiation characteristic owing to its symmetric structure and achieves gains to be 2.44, 3.74, 3.3, and 2.02 dBi at 2.4, 3.5, 5.2, and 5.8 GHz, respectively. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 1283,1286, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25197 [source] A compact multiband antenna based on CRLH-TL ZOR for wireless mobile systemMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 12 2009Jeong Keun Ji Abstract A compact multiband antenna using a composite right/left-handed transmission line (CRLH-TL) zeroth-order resonator (ZOR) for global system for mobile communications (GSM900/1800/1900, 880-960/1710-1880/1850-1990 MHz), wideband code division multiple access (WCDMA, 1920,2170 MHz), and wireless broadband (WiBro, 2.3,2.4 GHz) operations is presented. The proposed antenna having a total volume of 35 mm × 5 mm × 3 mm comprises a lower band ZOR antenna part and an upper band ZOR antenna part. The zeroth-order resonant properties are described and analyzed using dispersion diagrams based on the CRLH-TL ZOR theory and the full-wave simulation. The radiation patterns are the same as the omnidirectional characteristics and the maximum gains are 1.64, 2.47, and 3.32 dBi at 0.92, 1.88, and 2.2 GHz, respectively. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 2852,2855, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24799 [source] A low cost miniaturized circularly polarized antenna for UHF radio frequency identification reader applicationsMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 10 2009Zhongbao Wang Abstract A low cost miniaturized CP antenna is proposed for UHF RFID (Radio Frequency Identification) reader applications. The antenna is composed of a vertical ground and a square-ring patch with truncated corners. A novel capacitively coupled feed structure is proposed for good impedance matching. The antenna has S11 < ,20 dB and a gain level of about 6.9 dBi at 920,925 MHz (Chinese RFID band). Comparing to the conventional CP antenna, the size of the proposed antenna can be reduced by 33%. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 2382,2384, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24612 [source] A compact triple-band antenna design for UMTS, WLAN and WiMAX applicationsMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 9 2009Jhin-Fang Huang Abstract A compact triple-band planar antenna applied to UMTS, WiFi and WiMAX applications is proposed. The proposed antenna provides three wide frequency bands, which are 1744,2759 MHz, 3271,4126 MHz and 4718,5908 MHz, realized in a commercial FR4 printed- circuit board (PCB) with a permittivity of 4.4 and thickness of 0.6 mm. Both simulation and measurement are pretty matched and indicate that the proposed antenna achieves gains to be 3.5, 3.0, and 2.5 dBi at 2.4, 3.5, and 5.2 GHz, respectively. The antenna dimension is 52.8 × 31.2 mm2, smaller than presently published antennas discussed in comparison table. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 2207,2212, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24522 [source] Substrate-integrated-waveguide feed network for microstrip antenna arraysMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 7 2009Mohsen Yousefbeigi Abstract In this article, a low-loss parallel-series feed structure using substrate integrated waveguide (SIW) technology for a single-layer microstrip antenna array is presented. In addition to reduction of feed radiation, the feed network benefits from typical advantages of planar structures such as compactness, low cost, integrability, and mass-producibility. A 2 × 8 microstrip antenna array of size 109 mm × 34 mm fed by the proposed SIW feed system is designed and fabricated. Measurements on the fabricated array verify a minimum gain of 17.5 dBi in the frequency range of 17.4 to 18 GHz. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 1619,1621, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24412 [source] Wideband circularly polarized cavity-backed crossed loop antennaMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 7 2009Shi-Wei Qu Abstract A circularly polarized cavity-backed crossed loop antenna is proposed in this article. The optimized overall dimensions of the antenna are 1.13,o in diameter and 0.267,o in height (,o is the free-space wavelength at the center frequency), and the circumference of one loop is 1.1,o. Measurements show that the proposed antenna features an 81% impedance bandwidth for SWR ,2, a 40% bandwidth for axial ratio ,3 dB, an average gain of 10 dBi, and stable radiation patterns over the whole band from 1.42 to 2.13 GHz. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 1714,1718, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24406 [source] A compact dual-band modified T-shaped CPW-fed monopole antennaMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 4 2009R. Sujith Abstract A compact, dual band coplanar waveguide fed modified T-shaped uniplanar antenna is presented. The antenna has resonances at 1.77 and 5.54 GHz with a wide band from 1.47,1.97 GHz and from 5.13,6.48 GHz with an impedance bandwidth of 34% and 26%, respectively. Also the antenna has an average gain of 3 dBi in lower band and 3.5 dBi in higher band with an average efficiency of 90%. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 937,939, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24249 [source] An integrated packaging antenna-diplexer module for cellular/SDMB bands with LTCC technologyMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 4 2009Jeung Uk Ha Abstract This article presents an integrated packaging antenna-diplexer module for wireless communication system in the cellular and satellite digital multimedia broadcasting (SDMB) band. Multilayer low temperature cofired ceramic (LTCC) technology with integration capability was used in design and fabrication of the proposed module. To achieve a compact integration, an inverted-F antenna (IFA) with a meander line and a diplexer composed of low-pass filter (LPF) and high-pass filter (HPF) was embedded. The proposed module with dimension of 27.5 × 12.0 × 2.2 mm3 operates over a range from 813 to 902 MHz for the cellular band and from 2586 to 2655 MHz for the SDMB band. An isolation level below ,25 dB was obtained at each band. The measured gains of the fabricated module are ,1.96 and ,5.43 dBi, respectively. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 1039,1043, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24244 [source] Efficient electrically small loop antenna using SRR structure on the ground planeMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 1 2009Joong-Kwan Kim Abstract In this article, an electrically small loop antenna using capacitive loading is proposed. The loop antenna acts as an inductive element and the gap between two lines of SRR in the ground plane acts as a capacitive element; hence the combined system with these two elements is operated as a LC resonator. The equivalent circuit model of the antenna structure is applied to analyze and qualify the design correctness. Although the proposed antenna has a very small size, it shows a good performance. The measured maximum gain and radiation efficiency of the fabricated antenna at the frequency of 2.04 GHz are 3.6 dBi and 81.02%, respectively. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 201,204, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24016 [source] High gain cavity-backed slot antenna with a windowed metallic superstrateMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 12 2008M. A. Hanqing Abstract A novel technique for gain enhancement of cavity-backed slot antenna is developed and discussed. The high gain radiation of the proposed antenna is achieved by a windowed metallic superstrate above the slot. The parametric studies of the proposed structure are provided, the radiation mechanism of the proposed antenna is investigated, and then the design guidelines for this type of radiators are described. The prototype is fabricated and found to have an impedance bandwidth of 12% and a gain of 12.3 dBi at the center frequency of 2.4 GHz. The characteristics of the proposed antenna have been validated by CST simulation software and experiments. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 3114,3118, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23880 [source] Planar 4-element UWB antenna array and time domain characterizationMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 12 2008Ying-Ying Yang Abstract In this article, a novel planar ultra-wideband (UWB) antenna array based on four identical UWB antenna elements for UWB applications is presented. The proposed antenna array yields an impedance bandwidth of 3.1,10.6 GHz with VSWR <2. Over the entire bandwidths, it has constant high gain, which is about 6.5,10.5 dBi, and a 60° 3-dB beamwidth is obtained within the operational band. A planar 2-element UWB antenna array and a band-notched 4-element UWB antenna array are also provided for references. Time domain descriptors of the proposed antenna array have been used to estimate short-range UWB signal transmission, propagation, and reception. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 3118,3123, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23874 [source] Circularly polarized stacked antenna with a high-impedance ground plane for RFID reader applicationsMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 9 2008Jwo-Shiun Sun Abstract A circularly polarized (CP) stacked antenna for the long range reader of a RFID is studied. The proposed CP antenna using stacked patch technique with a high-impedance ground plane exhibits fairly good performances of 30 MHz bandwidth for 3 dB axial ratio, 70 MHz bandwidth referred to 10 dB return loss at the center frequency of 915 MHz. The gain of the designed antenna is more than 7 dBi over 902,928 MHz and 922,928 MHz and the reading range of the reader reaches 5.5 m. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 2248,2250, 2008; Published online in Wiley InterScience (www.interscience.wiley.com).DOI 10.1002/mop.23658 [source] Small microstrip patch antennas with short-pin using a dual-band operationMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 2 2008Cheol Yoon Abstract This article presents the design and fabrication of a short-pin dual-band E-shaped microstrip patch antenna for application in a 2.630,2.655 GHz band satellite-DMB with a 5.725,5.825 GHz band wireless LAN. The prototype consist of a short-pin and E-shaped patch. To obtain sufficient bandwidth in VSWR < 2, an air layer is inserted between the ground plane and the substrate. A small short-pin patch that has a dual-band characteristic is used. Important design parameters are the slot's existence, length, the air-gap's height, the feed point's position, and the short-pin's existence and point position. From these optimized parameters, an E-shaped antenna is fabricated and measured. The measured results of the fabricated antenna are obtained individually at 200 and 700 MHz bandwidths in VSWR < 2 referenced to the center frequency, and the individual gain at 8.79 and 10.26 dBi. The experimental 3 dB beam width is shown to be broad across the pass band in the E-plane, and in the H-plane is individually 73°, 65°, 74°, and 42°, respectively. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 367,371, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23099 [source] CP-microstrip coplanar patch antenna for satellite receptionMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 2 2008Wojciech J. Krzysztofik Abstract A design of a broadband circularly polarized coplanar-square-patch antenna, CSPA, for Iridium satellite reception via handset is proposed and experimentally studied. With the introduction of some asymmetry in the structure to a single-feed coplanar-sqaure-patch microstrip antenna, it is possible to excite two orthogonal degenerate resonant modes for circular polarization (CP) radiation. Experimental results of constructed prototypes show that the obtained 3-dB axial-ratio bandwidths can reach as large as 8.5%. The proposed antenna has a peak antenna gain of about 4.2 dBi, with efficiency 85% for frequencies within the CP. Some prototypes of the proposed CP design CSPA antennas have been implemented and experimental results are presented and discussed. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 372,375, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23071 [source] A circular CPW-FED slot antenna for broadband circularly polarized radiationMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 11 2007I-Chung Deng Abstract The design of a circular slot antenna for obtaining broadband circularly polarized (CP) radiation using a coplanar waveguide (CPW) feed is presented. The operation of the proposed antenna is achieved by protruding metallic mono-strip from the circular ground plane towards the slot center at , = 0° and feeding antenna using a 50-, CPW with a protruded single strip at , = 270°. In this design, the impedance bandwidth and 3 dB axial-ratio bandwidth can reach as large as 50 and 36%, respectively. The peak of antenna gain is about 3.9 dBi, with gain variations <1 dBi for the frequencies within CP bandwidth. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 2728,2733, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22881 [source] A novel internal antenna with high gain for wireless phoneMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 9 2007Ying Liu Abstract A novel internal antenna for synchronous code division multiple access band wireless phone is presented. Traditional internal antenna is monopole or Planar Inverted-F Antenna, which have no gain high enough in the limited space in phone. The proposed antenna is composed of two antenna elements with equal magnitude and 180° phase difference, to assure voice quality with high gain. The measured maximum gain is 2.69 dBi and maximum efficiency is 70.1% in the frequency band 450,470 MHz. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 2112,2114, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22708 [source] The small UWB hybrid antennaMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 9 2007Yi-Wah Chan Abstract A small size end-fire mode hybrid monopole/DR antenna is introduced and tested. The hybrid antenna combines an annular DRA and a quarter-wave monopole antenna to perform ultrawideband response. The proposed technique is used to reduce the length of monopole antenna and improve the whole impedance bandwidth. The maximum gain and impedance bandwidth is 5.5 dBi and 100% (VSWR , 2), respectively. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 2157,2159, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22693 [source] | ||||||||||||||||