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Selected AbstractsA T-type fractal boundary single-feed circularly polarized microstrip antennaINTERNATIONAL JOURNAL OF RF AND MICROWAVE COMPUTER-AIDED ENGINEERING, Issue 2 2009P. Nageswara Rao Abstract A single-feed T-type fractal boundary microstrip antenna is presented. It is established that a very good circular polarization is realizable with 3-dB axial ratio bandwidth of 1.27% at the center frequency of 2446 MHz by changing the electrical length in two directions of the square patch by using T-type fractal curve as boundary. Further it is shown that the surface area occupied by the antenna is reduced compared to the Euclidean shaped patch antenna without much degradation in gain of the antenna. Experimental results are compared with simulated results and a very good agreement is obtained. © 2008 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2009. [source] Characteristic analysis of reverse-L-shaped microstrip-fed large-bandwidth printed slot antennaINTERNATIONAL JOURNAL OF RF AND MICROWAVE COMPUTER-AIDED ENGINEERING, Issue 6 2002Yong-Woong Jang Abstract The characteristics of a reverse-L-shaped microstrip-fed structure is analyzed using the finite difference time domain method, and the characteristics of the proposed antenna are compared with a conventional antenna. The return loss, radiation resistance, and voltage,standing wave ratio in the frequency domain are calculated by Fourier transforming the time domain results. When the proposed feed structure is used, the bandwidth is extended in proportion to the slot width and the radiation resistance has the low value. When the slot width is 16 mm, the experimental bandwidth is approximately 50% (,10 dB , S11) at the center frequency of 2.3 GHz. In addition, the experimental data for the impedance and radiation pattern of the antenna are described. They are in good agreement with the calculated results. © 2002 Wiley Periodicals, Inc. Int J RF and Microwave CAE 12, 496,502, 2002. Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mmce.10055 [source] An optimum superconducting ultra-wideband bandpass filter at VHF bandMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 12 2010Wei Chen Abstract A highly selective superconducting ultra-wideband filter with a passband from 125 to 260 MHz is designed and demonstrated using a microstrip structure. The filter is designed according to a circuit model for an optimum short-circuited stub transmission-line filter and consists of 10 shunt short-circuited stubs separated by connecting lines. The short-circuited stubs are quarter-wavelength long, and the connecting lines are half-wavelength long. The filter is realized on two 3-inch YBCO/LaAlO3 substrates, which are connected by two bonding wires. The short-circuited stubs are grounded via two grounding pads that are attached to the box wall by a number of SiAl bonding wires. The measured results exhibit a selective filtering characteristic equivalent to a 19-pole Chebyshev filter and a low insertion loss of less than 0.1 dB at center frequency without tuning. Furthermore, the experimental results of the filter are in good agreement with the simulated ones. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52:2639,2641, 2010; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.25571 [source] Bandwidth enhancement of a coplanar waveguide-fed asymmetrical slot antenna with a rectangular patchMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 10 2010Shou-Tao Fan Abstract A coplanar waveguide-fed asymmetrical slot antenna with a rectangular patch for bandwidth enhancement is demonstrated. By attaching a rectangular patch to the monopole radiating element, a good performance of bandwidth enhancement for the antenna is achieved. From simulational and experimental results, the enhanced impedance bandwidth of the proposed antenna, defined by ,10 dB return loss, can reach 13.1 GHz, from 2.4 to 15.5 GHz, or about 146% with the center frequency 8.95 GHz, which makes it an excellent candidate for the ultra wideband (UWB, 3.1,10.6 GHz) applications. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52:2259,2261, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25476 [source] Wideband spurious suppression of dual-mode band-pass filter using defected cascaded resonatorsMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 8 2010Hung-Wei Wu Abstract This article presents a new design of wideband spurious suppression of dual-mode band-pass filter (BPF) using defected cascaded resonators (DCRs). The pattern of the DCRs is similar with that of the conventional low-pass stepped impedance resonator, whereas it is etched in the ground. It is verified that adding DCRs in planar BPF can effectively provide a very wideband range for spurious suppression. The dual-mode BPF is designed at center frequency (f0) of 5.2 GHz, and has a very wideband spurious suppression below 30 dB as far as over 5f0 when using the DCRs. The measured results have a good agreement with the EM simulated results. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 1694,1697, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25332 [source] Triple-band compact printed dipole antenna with wideband integrated balun for WLAN/WiMAX applicationsMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 7 2010Qiu-Yi Zhang Abstract A triple-band dipole antenna with wideband balun integration is proposed in this article. This antenna consists of two dipoles, a wideband balun and feeding line. These three parts are integrated into a compact design, which has a small size of 30 × 25 × 0.8 mm3 based on the substrate having a dielectric constant of 2.55. The simulated results show that triple bands of 2.40,2.59 GHz, 3.42,3.80 GHz, and 5.06,5.95 GHz are attained by this antenna, and can cover the bands of WLAN/WiMAX. The simulated and measured radiation patterns at different center frequency are also demonstrated and the designs of dipoles and balun are also provided, which exemplify omnidirectional characteristics in the H -plane. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 1619,1622, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25265 [source] C-shaped ultra-wideband bandpass filter with WLAN notch bandMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 5 2010Pai-Yi Hsiao Abstract A compact bandpass filter (BPF) embedded with 5.8 GHz wireless-LAN notch is presented for 3.1,10.6 GHz ultra-wideband (UWB) systems. The proposed UWB-BPF based on a defect-grounded structure is implemented with an FR4 board. Two open-loop resonators on the top layer provide a narrow notch band whose center frequency can be easily adjusted by varying the sizes of the open-loop. A simple C-shaped slot on the bottom ground layer is adopted to improve the bandwidth performance. The characteristics of UWB-BPF are analyzed and simulated using a circuit model of LC lump elements. The size of the filter is at least 34% less than those filters with the same specification. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 1215,1218, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25153 [source] Fast and accurate calculation of transmission coefficients for an EBG microstrip structureMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 4 2010Shao Ying Huang Abstract In this article, an approach is proposed to provide an accurate and fast calculation on the transmission coefficients of an electromagnetic band-gap (EBG) structures where patches are periodically inserted into the microstrip line (capacitive loaded EBG microstrip structure). The stopband performance, such as the center frequency, bandwidth, and attenuation, of these EBG structures can be predicted at a high degree of accuracy through the calculation of the transmission coefficient. The dispersion relation of electromagnetic waves in the structure is derived, plotted, and analyzed. The grating nature of the structure is demonstrated. This approach can be applied to periodic microstrip structures of a similar nature to simplify the analysis and design procedures. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52:793,797, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25046 [source] Microstrip ring resonator bandpass filters using ceramic substrateMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 1 2010Yuan-Bin Chen Abstract The miniaturization of ring bandpass filters by employing high-permittivity ceramic substrates (with respective dielectric constants of 9.7 and 23.5) are investigated. Microwave dielectric ceramics with high permittivity are commonly applied in several microwave communication components. With the advantages of compact size, high-permittivity ceramics can be used as the substrate for bandpass filters. Moreover, the fundamental characteristics of newly developed compact square-ring resonators have also been described and applied to the design of bandpass filters. In this paper, the designed square-ring resonators structures are simulated using an IE3D simulator. The responses of the fabricated bandpass filters using Al2O3 (,r = 9.7, tan , = 0.000036) and 0.875Mg0.95Zn0.05TiO3 -0.125Ca0.8Sm0.4/3TiO3 (,r = 23.5, tan , = 0.000021) ceramic substrates are designed at the center frequency of 2.4 GHz. This compact size, low loss bandpass filter should be useful in many wireless communication systems. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 218,220, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24847 [source] Compact dual-mode bandpass filter using arrow-shaped slot resonatorMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 12 2009Youngje Sung Abstract A novel design of a compact bandpass ring slot filter for achieving dual-mode operation is proposed and experimentally studied. By using an arrow-shaped slot structure as a resonator, the resonant frequency of the proposed filter is significantly lowered, which can lead to a large filter size reduction for a fixed frequency operation. Two degenerate modes are achieved by loading with proper asymmetry, which can be placed at the corner of diagonals. A prototype of the proposed design is implemented and measured. From the measured results, the proposed filter has about 5.2% bandwidth at the center frequency of 0.97 GHz and a minimum insertion loss of 1.07 dB within passband. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 2989,2991, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24809 [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] Bandpass filter modeling employing Lorentzian distributionMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 5 2009Mahmoud Al Ahmad Abstract This letter takes a close outlook of modeling a bandpass filter performance with the Lorentzian distribution function. Lorentzian function parameters are correlated with the filter parameters, namely, its bandwidth and center frequency. The zeros and poles of the filter are extracted from the closed form expression of the Lorentzian function, which is used to construct the rational model of the filter. This procedure is expected to optimize the overall filter performance and to construct a consistent equivalent circuit from its computed poles and zeros. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 1167,1169, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24288 [source] 60-GHz bandpass filter with ACMRC resonator fabricated using 0.18-,m CMOS technologyMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 3 2009Chia-Hsieh Liu Abstract This article presents design and implementation of a 60-GHz millimeter- wave on-chip bandpass filter using a 0.18-,m standard CMOS process. The asymmetric compact microstrip resonator cell structure is used to design the filter with two transmission zeros. The input and output capacitors using multilayer coupling are added to create the passband. The die size of the chip is 0.85 × 0.64 mm2. The filter has a 3-dB bandwidth of about 15 GHz at the center frequency of 64 GHz. The measured insertion loss of the center-frequency is about 3.9 dB and the return loss is better than 10 dB within passband. The designed on-chip filter is useful for the integrated design of the 60-GHz CMOS single-chip RF transceiver. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 597,600, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24119 [source] A shorted square-ring slot antenna with a branched slot for the 1575 MHz and 2.4 GHz dual-band operationsMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 2 2009Chin-Long Tsai Abstract A shorted square-ring slot antenna with a branched slot is presented for the 1575 MHz and 2.4 GHz dual-band operations. This proposed antenna can be designed by two steps. First, the shorted square-ring slot antenna is designed for circular polarization in the GPS band. Then, a branched slot is added to the original structure to result linear polarization in the 2.4 GHz band. Because the added branched slot almost has no influence in the GPS band's characteristics, the design rule is very simple. The impedance and axial ratio bandwidths for the GPS band is 23.3% and 4.2%, respectively. Besides, the AR and antenna gain is 1.23 dB and 2.3 dBic at the frequency of 1575 MHz. The impedance bandwidth for the 2.4 GHz band is 4.5% and antenna gain at the center frequency of 2.445 GHz is 2.8 dBi. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 402,405, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24073 [source] A reduced-size branch-line coupler for improved LDMOS balanced power amplifiersMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 2 2009Drasko Draskovic Abstract This article discusses the application of a reduced-size branch-line coupler in the design of a LDMOS class-AB balanced power amplifier at a center frequency of 2.14 GHz. In the proposed balanced configuration, at center frequency a size reduction, improved intermodulation distortion level by 7 dB, and power added efficiency by 5% are achieved, comparing with the balanced configuration with Wilkinson couplers. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 445,448, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24058 [source] Small antennas application in portable phonesMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 12 2008Sheng-Yi Huang Abstract The compact antennas are introduced, which are working in universal mobile telecommunication system (UMTS) of 1920,2170 MHz and digital video broadcast-handheld (DVB-H+) of 1452,1492 MHz for portable phones applications. The resonant frequency of UMTS is presented by using a planar inverted-F antenna (PIFA) element. The other resonant frequency of DVB-H+ is presented by using meander-line configurations. The ratio of impedance bandwidth of the PIFA antenna to the center frequency 1500 MHz is 29% (DVB-H+). The ratio of impedance bandwidth of the meander radiator to the center frequency 2100 MHz is 20% (UMTS). The size of the two antennas is shortened to 65% compared to general internal radiators. The total volume of the two radiators is 40 (L) × 5 (W) × 0.2 (H) mm3 (PIFA) and 20 (L) × 5 (W) × 0.2 (H) mm3 (meander radiator), respectively. The experimental results are compared to the numerical simulation, high-frequency structure simulator, for agreement. The good performances of the antennas like wide bandwidth and omnidirectional far-field patterns can be obtained. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 3020,3023, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23872 [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] A CMOS Colpitts voltage controlled oscillator with an enhanced transconductance methodMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 12 2008Ching-Ian Shie Abstract This work presents a technique to enhance the performance of the conventional PMOS Colpitts VCO circuit. This technique is accomplished by adding an NMOS cross-coupled pair under the traditional differential Colpitts VCO to enhance the oscillator startup condition. The signal analysis also supports this viewpoint and presents a device-choosing method to optimize the output power and phase noise. In realization, the circuit in the CMOS 0.18-,m technology, a U-shaped inductor, and thick oxide varactors are adopted in circuit to increase the quality factor of resonant tank. The performance of VCO demonstrates a center frequency of 16.7 GHz, a FOM of ,186.2 dBc/Hz, and the phase noise of ,110.42 dBc/Hz at the 1 MHz offset from the oscillation frequency. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 3160,3164, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23944 [source] A compact wideband parallel-strip 180° hybrid couplerMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 12 2008L. Chiu Abstract In this study, a wideband compact parallel-strip 180° hybrid coupler with the center frequency of 2 GHz is presented. By replacing the 270° section in the 180° hybrid coupler with a parallel-strip phase reversal swap, the total circuit size is reduced by half. In this structure, the phase gradients of the four arms of the coupler are equalized; therefore, the operation bandwidth is dramatically enhanced. S-parameters of the coupler are simulated and measured with good agreement. As predicted from the measured data, the bandwidth of the 90% combining efficiency is increased from 45 to 124%. The proposed design achieves more than ,25 dB signal suppression within the whole measured frequency range (0,4 GHz) as opposed to 1.8 to 2.2 GHz of the conventional design. The proposed 180° hybrid coupler can serve as a wideband in-phase/differential power divider/combiner, which are essential for many RF and microwave subsystem designs. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 3271,3274, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23926 [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] Adaptive TRX isolation scheme by using TX leakage canceller at variable frequencyMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 8 2008Jin-Woo Jung Abstract This article presents a TX leakage cancellation scheme for UHF RFID readers. A prototype is implemented on a UHF RFID reader board, which includes a circulator, directional coupler, microcontrol unit (MCU)-controlled variable attenuator, and phase shifter. The difference between a conventional TX leakage canceller and this new one is that, reflected signals caused by mismatches between the front-end and the antenna are included; in addition, high isolation is supplemented at variable frequencies. About 10% of the frequency range is recovered by the best suited parameter values that provide a predetermined process of MCU; and thus, peak isolation characteristics are constantly guaranteed at each center frequency by phase-shifted signal generation that follows references stored in MCU. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 2043,2045, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23592 [source] Trisection cross-coupled filter with symmetrical response using split-ring resonator DGSMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 7 2008Bian Wu Abstract In this article, a novel trisection cross-coupled filter with symmetrical response by using split-ring resonator defected ground structure (SRR DGS) is presented. The SRR DGS is loaded at the bottom of a two-pole microstrip SRR filter, then a compact trisection cross-coupled filter with a pair of transmission zeros is obtained. A practical filter which has a center frequency of 1.4 GHz and a relative bandwidth of 14% is successfully designed and fabricated. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1774,1776, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23529 [source] A novel crossed slotted patch dual-mode bandpass filter with two transmission zerosMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 3 2008Sean Wu Abstract This article presents a miniaturized dual-mode bandpass filter (BPF) with two transmission zeros and low insertion-loss using crossed slotted patch resonator. The BPF is mainly formed by a ,/2 patch resonator which is a pair of crossed slots with unequal widths is embedded in the center. By tuning the perturbation element, which resulted from the unequal slot widths along the diagonal, two resonant modes are excited and a pair of transmission zeros are generated to improve the selectivity of the BPF performance. The proposed filter at center frequency (f0) of 1.55 GHz has very good measured characteristics including the bandwidth of 1.49,1.62 GHz (3-dB fractional bandwidth of 8.4%), low insertion loss of 1.74 ± 0.35 dB. The measured filter performance is in good agreement with the simulated response. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 741,744, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23219 [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] A compact spiral stripline-loaded monopole antenna with a vertical ground planeMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 1 2008Truong Khang Nguyen Abstract In this letter, we propose a compact spiral stripline-loaded monopole antenna on a vertical ground plane. The measured results show that the antenna has a fractional bandwidth of 12.1% for a voltage standing wave ratio (VSWR) less than 2 at the center frequency of 1.10 GHz, as well as a good omni-directional radiation pattern. The small size of 0.04 ,o × 0.04 ,o × 0.04 ,o makes it promising for use as an internal antenna in mobile handsets. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 250,252, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23043 [source] A novel four-stages double-layered dielectric waveguide bandpass filter in LTCCMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 8 2007Fei Liang Abstract This study presents a novel four-stage double-layered waveguide bandpass filter and its simulation method. The longitudinal size of the waveguide filters is reduced by 50% due to the application of double-layered structure. The four-stage double-layered bandpass filter with a 8.8 mm length, 6.2 mm width, and 1.6 mm height is manufactured by LTCC. It has a center frequency of 5.21 GHz, bandwidth of 300 MHz, pass-band ripple of 0.1 dB, and insertion loss of 0.8 dB, which shows miniaturization, low insertion losses and meets the demand of next generation of WLAN system. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 1837,1840, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22587 [source] A broadband microstrip Marchand balun with vertical coupling structureMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 4 2007Hee Nam Abstract In this paper, a broadband microstrip Marchand balun is presented. It is implemented by new vertical coupled structure, which is suggested to improve the coupling effect in the conventional coupler. Using this vertical coupling structure, the Marchand balun shows broad bandwidth of larger than 115% at the center frequency of 2.3 GHz. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 752,755, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22281 [source] Design of parallel coupled-line microstrip wideband bandpass filter using stepped-impedance resonatorsMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 4 2007Cheng-Yuan Hung Abstract In this article, a parallel coupled-line microstrip wideband bandpass filter (PCM-WBF) using stepped-impedance resonators (SIRs) is designed and implemented on commercial printed circuit board (PCB) of RT/Duroid 5880 substrate. The first two resonant modes of the SIR are coupled together and they are applied to create a wide passband. The proposed filter at center frequency f0 of 5.76 GHz has very good measured characteristics including a bandwidth of 3.63,7.92 GHz (3-dB fractional bandwidth of 74%) and a low insertion loss of ,1 ± 0.9 dB. Experimental results of the fabricated filter show a good agreement with the predict results. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 795,798, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22260 [source] A hairpin line wideband bandpass filter design with embedded open stubsMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 4 2007Cheng-Yuan Hung Abstract In this paper, a compact three-poles hairpin line wideband bandpass filter with several embedded open stubs to improve the stopband is designed and implemented on print circuit board substrate. This filter at center frequency f0 of 4.25 GHz has presented almost very good measured characteristics, including the bandwidth of 3.1,5.4 GHz (3-dB fractional bandwidth of 54%), low insertion loss of ,0.7 ± 0.4 dB, sharp rejection due to two transmission zeros in the passband edge created by interstage coupling, and wide stopband rejection greater than 15 dB from 5.6 to 11 GHz. Experimental results of the fabricated filter show a good agreement with the predict results. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 934,936, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22302 [source] Microstrip-fed slot antennas backed by a very thin cavityMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 1 2007Andrea Vallecchi Abstract Slot antennas with a backing cavity for unidirectional radiation are investigated with the aim of achieving a thin structure capable of reasonably broadband operation. By tuning together the slot length and the cavity cross-section, a very low-profile cavity-backed slot (CBS) is demonstrated. The cavity thickness of this slot antenna is about 10 times smaller than conventional one-quarter wavelength cavities, which would allow constructing this antenna even with standard cost-effective multilayer planar technology. The high gain and fairly wideband operation are the major advantages of the proposed configuration, which features a bandwidth of about 10% at a center frequency of 1.8 GHz with radiation efficiency in excess of 80%. Measured data are presented and compared with simulation results obtained by both the method of moments (MoM) and the finite integration technique (FIT). © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 247,250, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22073 [source] | ||||||||||