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A novel design of double-ring slot antenna with tree-shaped coupling strip for 2.4/5-GHz dual-band applications is presented in this paper. Two concentric slot rings are proposed in order to determine the certain resonated frequencies of two desired bands (5.20–5.55 and 5.55–5.80 GHz) and the inner circular disk depicts the range of 2.27–2.51 GHz. A tree-shaped coupling strip is designed with branches to couple the inner circular disk and with leaves to couple the double ring slot, respectively; therefore, it can simultaneously enhance the bands' responses using impedance-matching techniques. This is a compact microstrip antenna for IEEE 802.11a/b WLAN applications. The simulated and experimental results for the frequency responses, radiation patterns, and current distributions are presented and discussed. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 47: 374–379, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21173 [ABSTRACT FROM AUTHOR]

This paper addresses experimental RF performance evaluation, and electrical-parameter extraction of different-size ferroelectric varactor shunt switches. Ferroelectric varactor shunt-switch operation is based on the nonlinear dielectric tunability of a Ba0.6Sr0.4TiO3 (BST) thin film sandwiched between two metal layers in a parallel-plate configuration. Coplanar-waveguide implementation of the varactor shunt switch results in a high-speed RF switch, through a simple two-metal layer Si MMIC compatible process on high-resistivity Si substrates. The experimental RF performance of the switches shows low insertion loss for smaller-area devices, with good isolation for larger-area devices. To optimize the device design, the rf performances of multiple devices are tested, and the electrical parameters are extracted. The capacitance of the varactor shunt switches tested are tunable by more than 4:1 for bias voltages below 12 V. The switching speed of the devices tested is approximately 43 ns, based on the step-response measurements. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 47: 370–374, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21172 [ABSTRACT FROM AUTHOR]

This paper presents the design of two filters at a center frequency of 1 GHz using a novel type of ring resonator. Their advantage over conventional microstrip ring resonators lies on their lower-frequency sensitivity to substrate thickness due to the addition of interdigital capacitors that concentrate the electric field near the surface. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 47: 381–384, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21175 [ABSTRACT FROM AUTHOR]

A novel method, the finite-element method (FEM) using Fourier series as the interpolating function, is presented in this paper for calculating the quasi-static characteristics of coupled cylindrical striplines and microstrip lines filled with multilayered dielectrics. This method is very similar to the normal FEM, but has a much lower-order matrix equation, smaller computational contents, and higher accuracy. It is simpler and more flexible for application than the conformal transformation method. Compared with the integral-equation and spectral-domain methods, this new method is more obvious with regard to its physics and, also, it is not involved in the difficult task of selecting the base functions and relative convergence. The numerical results shown here for several examples are in good agreement with those in the references. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 47: 265–270, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21143 [ABSTRACT FROM AUTHOR]

This paper presents the design of a thinned reflectarray. The phase-shifting elements are slotted rectangular microstrip antennas with via connection to the ground plane. They are disposed in a regular grid. The thinning procedure is used to determine which elements may be removed, according to the desired radiation pattern, without significant change in directivity. For this approach, a genetic algorithm is proposed. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 46: 559–562, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21050 [ABSTRACT FROM AUTHOR]

A microstrip patch antenna with a 2D multiperiod electromagnetic band gap (EBG) sandwiched between the patch and the ground plane is proposed and studied in this paper. The proposed models are assessed using finite-difference time-domain (FDTD) simulations and experimental measurements. The simulated and measured results show that, with the sandwiched multiperiod EBG structure, the microstrip patch antenna can achieve wider impedance bandwidth and higher gain than the sandwiched single-period EBG structure. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 46: 437–440, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21010 [ABSTRACT FROM AUTHOR]

Design and development of a photonic bandgap (PBG)-assisted shared-aperture dual-band orthogonal aperture-fed rectangular microstrip patch antenna element, which is suitable for a portable very small aperture terminal (VSAT), are presented in this paper. The dual-band dual-polarized antenna element achieves 21% input impedance bandwidth at the S- and C-bands. A comparison of the antenna with and without 2D PBG grids shows that the inclusion of PBG structures (PBGSs) improves the antenna performances. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 46: 289–292, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20968 [ABSTRACT FROM AUTHOR]

The novel design of a T-coupled circular microstrip antenna with H-shaped aperture for active reflectantenna application is presented in this paper. The circular patch determines the frequency resonated; the H-shaped aperture is used to obtain the responses of the desired 2.4–2.48 GHz ISM band and the T-coupled feed line enhances the response of the band using the impedance-matching technique. Meanwhile, the dual-polarized ports of the T-coupled microstrip antenna are developed for the active reflectantenna and applied to a corner-wall structure. The antenna is capable of achieving high-directivity gain, wide bandwidth, high isolation, and low cross-polarization levels. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 46: 120–125, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20919 [ABSTRACT FROM AUTHOR]

In this paper, a variable-width meander-slot antenna fed by CPW is proposed for the use in miniaturized personal-communication devices. By optimizing the slot width of the antenna, we design a uniplanar antenna that is 8% to 12.3% of the size to a conventional rectangular microstrip patch antenna. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 46: 188–191, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20940 [ABSTRACT FROM AUTHOR]

This paper presents the design of a wideband 16 × 4 element array of a microstrip-proximity-fed rectangular-slot antenna for marine radar systems operating in the X-band. A wideband corporate-feed network is designed to feed the proposed array. The new design has a small size, a wide bandwidth of 52%, and good radiation characteristics in the entire operating band. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 46: 36–40, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20894 [ABSTRACT FROM AUTHOR]

This paper presents the measured reflected phase-variation curves for microstrip-patch elements of variable size, which form the most essential part in the design of a reflectarray antenna. A waveguide simulator exploiting the concept of infinite array is successfully implemented in the characterization of reflected phase, which avoids the need for large arrays for the empirical design of an element. A set of seven microstrip-array samples, each consisting of three square elements of the same size designed at 10 GHz, is measured. A comparison of the simulations using the finite-element method and the measured results shows good agreement. The phase variation is in the range of +167° to -178° for a patch-size variation of 5.5 to 13 mm. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 45: 528–531, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20869 [ABSTRACT FROM AUTHOR]

This paper presents a novel design of printed circular-ring monopole antennas for ultra-wideband (UWB) applications. A circular-disc ring printed on a dielectric substrate and fed by a 50Ω microstrip line is demonstrated numerically and experimentally to achieve an ultra-wide 10-dB bandwidth with omnidirectional radiation patterns over the entire bandwidth. The design parameters and the performance of the proposed antenna are analyzed. Good agreement has been obtained between the simulation and the measurement. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 45: 372–375, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20827 [ABSTRACT FROM AUTHOR]

This paper presents the probe-fed center-slotted suspended plate antennas (CS-SPAs) with capacitive and resistive loading. The impedance and radiation characteristics of the proposed antennas, such as impedance bandwidth, gain, radiation patterns, and cross-pol radiation levels are investigated. The simulated results are validated by the measurements and compared with three other CS-SPAs fed by a single probe, short-circuited, and open-circuited loading, respectively. This study demonstrates an enhancement of impedance bandwidth and a decrease in gain with resistive loading, as compared to the CS-SPA with a shorting pin. The gains of CS-SPAs with plate-capacitor loading generally increase, with the same impedance bandwidth as that of the CS-SPA with a shorting pin. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 45: 355–360, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20822 [ABSTRACT FROM AUTHOR]

This paper presents a novel, compact, low-insertion-loss, sharp-rejection, wideband microstrip bandpass filter. The filter is based on a ring resonator with direct-connected orthogonal feed lines, and uses two stepped-impedance open stubs to construct a wideband passband with two sharp stopbands. The unit cell of the ring resonators is easily cascaded and also has the feature of a compact structure. The filter is designed to reduce interference in full-duplex systems for satellite communications. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 45: 312–315, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20807 [ABSTRACT FROM AUTHOR]

Parallel coupled-line bandpass filters using the ground-aperture technique are analyzed in this paper. A design guide and design curves for this kind of coupled-line bandpass filter on commonly used high- and low-permittivity substrates are presented. Based on the proposed design curves, two sample bandpass-filter configurations are designed. The design is simulated using Ansoft HFSS and validated by the measurements. Good agreement between the simulated and measured responses is obtained. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 45: 237–240, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20781 [ABSTRACT FROM AUTHOR]

An inverted microstripline-fed linear tapered slot antenna element and a design of its 16-element E-plane array are presented in this paper. The element is designed using the finite-difference time-domain (FDTD) method. The calculated results show that it has a wide-impedance bandwidth in the K-band. To investigate the E-plane array, the return loss at each element input port, the couplings among elements, and the array's radiation patterns are obtained using the FDTD method. Using a unique three-piece assembled structure, the array is fabricated and tested experimentally. The measured results show that it has a wide bandwidth and antenna efficiency. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 45: 241–246, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20784 [ABSTRACT FROM AUTHOR]

Knowledge of the mutual interaction between antenna elements is of great importance for the design of practical antenna arrays, especially for phased arrays and ultra-low side-lobe arrays. In this paper, to fully take into consideration the mutual coupling in an array environment, a mutual-impedance formula based on synthetic asymptote and variable separation [1] is used in an existing correction procedure in order to speed up the computation for microstrip patch arrays. The simulation results show that the performance of the finite microstrip patch arrays can be successfully predicted. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 44: 577–581, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20701 [ABSTRACT FROM AUTHOR]

This paper proposes a harmonic-suppression technique for a square microstrip-antenna design. In this study, the possible resonance at the 2nd and 3rd harmonic frequencies were effectively suppressed by adding loads to the antenna's feeding line, and the antenna performances for fundamental-mode operation were well retained. The design and experimental results are discussed and simple design principles for harmonic suppression of the proposed antennas are presented. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 44: 379–383, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20641 [ABSTRACT FROM AUTHOR]

In this paper, we investigate the theoretical behavior of microstrip antennas on tapered ferrite substrates. A full-wave analysis in the spectral domain is developed to provide antenna bandwidth enhancement as a function of linear variations in the substrate-height profile that supports the patch. The results for the main parameters are presented. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 44: 289–292, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20613 [ABSTRACT FROM AUTHOR]

This paper presents a method to suppress or eliminate the spurious responses of a BPF using interdigital-type resonators. The configurations presented employ interdigital-type resonators with one end grounded in order to realize improved BPF characteristics. The analysis shows that the configurations quite effectively suppress spurious responses up to five times the center frequency (5f0) and locate the attenuation poles in the stopband such that improved out-of-band characteristics can be realized. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 44: 126–130, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20565 [ABSTRACT FROM AUTHOR]

A cross-shaped microstripline-fed printed slot antenna with wide bandwidth is presented in this paper. The proposed antenna is analyzed using the finite-difference time-domain (FDTD) method. It was found that the bandwidth of the antenna depends highly on the characteristics of the proposed antenna, which depend highly on the design parameters (ls, Ws, offset,lu, and ld). We also compare the optimized offset/Ws ratio and the calculated bandwidth of RT-5880 substrate for slot width Ws. When Ws is 32 mm, the optimized offset/Ws ratio is 0.344, and the calculated bandwidth is 3.744 MHz (112.6%). The experimental bandwidth of this antenna is from 1.85 to 5.70 GHz, which is approximately 115.5%, for VSWR ≤ 2.0. The proposed antenna showed triresonance characteristics due to the wide bandwidth. Experimental data for the return loss and the radiation pattern of the antenna are also presented, and are in good agreement with the FDTD results. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 44: 162–165, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20576 [ABSTRACT FROM AUTHOR]

Recently, in order to satisfy the demand for precise and reliable global positioning system (GPS) applications, the dual-band circularly polarized (CP) antenna has been developed. This paper describes a new design of a probe-fed dual-band CP microstrip antenna with two corner-truncated square patches that overlap without an air gap. Compared with the conventional dual-band CP antenna with an air-gap layer between the two patches, the volume of this antenna is reduced and its fabrication is easier. Details of the proposed antenna design and experimental results are presented and discussed. The measured results confirm the validity of this design, which can meet the requirement of GPS application at 1575/1227-MHz frequencies. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 44: 58–61, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20547 [ABSTRACT FROM AUTHOR]

In this paper, we present a novel approach to improving the bandwidth of microstrip antennas using frequency-selective surfaces (FSSs) as an artificial magnetic ground plane (AMG). The micro-genetic algorithm (MGA) is employed to derive an optimal FSS element configuration that achieves the zero-phase condition for the reflection coefficient of an artificial surface at the desired frequency band. Two AMG configurations for single- and tri-band applications are designed by using the MGA, and their performances are compared with those of PEC ground-plane cases after integrating the AMGs with microstrip antennas. It is demonstrated that the use of such a surface, in lieu of the conventional PEC ground plane, leads to an improvement in the bandwidth of planar antennas that are placed above the surface. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 44: 6–13, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20532 [ABSTRACT FROM AUTHOR]

In this paper, we introduce a novel design for a high-directivity Electromagnetic Band Gap (EBG) resonator antenna that utilizes a frequency-selective surface (FSS) superstrate. The above type of superstrate is proposed as an alternative to an EBG type of dielectric superstrate—investigated previously by the authors—to reduce its height and facilitate the fabrication process. Although FSS superstrate and the patch antenna comprise a composite resonator, we begin by investigating the FSS structure characteristics first before dealing with the combination. We vary several important parameters, such as the distance between the FSS superstrate and the ground plane of the antenna, and the dimensions of the FSS superstrate, to determine their effect on the resonant frequency and the quality factor of the unit cell of the FSS. The above study enables us to derive some guidelines for an optimum array size of the FSS superstrate that eventually leads to a maximum directivity for the FSS antenna composite, as evidenced via a comparison of the quality factors of the FSS, the unit cell, and the composite. It is demonstrated that the directivity of the antenna with an optimized array size of the FSS superstrate increases by 17.29 to 24.92 dBi for three different strip-dipole lengths, as compared to that of the patch antenna alone (maximum 6 dBi). © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 43: 462–467, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20502 [ABSTRACT FROM AUTHOR]

This paper presents a compact microstrip low-pass filter with ultra-wide stopband and sharp cutoff frequency response. The conventional shunt open-stub filter with a slot on the ground plane has a wide stopband at high frequency, and the coupled open-stub microstrip filter has a sharp cutoff response at low frequency. The combination of these structures gives the filter the characteristics of an ultra-wide stopband and a prominent cutoff sharpness. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 43: 303–306, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20452 [ABSTRACT FROM AUTHOR]

Three microstrip miniaturized meanderline antennas for mobile communications are presented in this paper. Two-arm meanderline antennas, one with a patch and one with a rectangular loop, are fabricated and tested. The advantages of the antennas are the lower circuit cost, light antenna weight, short process time, a minimum number of via holes and simplified mechanical construction. In our experiments, comparisons of the radiated power and return loss of the three topologies of the meander-line antenna are presented. The loading effect of the outside environments surrounding the meander-line antennas is also discussed. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 43: 207–210, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20420 [ABSTRACT FROM AUTHOR]

We present a new application of uniplanar compact electromagnetic bandgap (UC-EBG) structures in antenna-beam shaping for indoor mobile communications. Such UC-EBGs are used to construct Fabry–Perot-type cavities in which the enhanced directivity can be achieved from conventional patch antennas. This paper demonstrates that an antenna beam can be shaped by shifting the defects (patch antennas) from the centre of UC-PBG cavities. The theoretical predictions are verified by numerical simulations and measurement results, and it appears that antenna-beam shaping in UC-EBG cavities can achieve the same radiation patterns as complex planar-antenna arrays used for improving the quality and strength of sent/received signals in mobile base stations. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 43: 108–112, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20391 [ABSTRACT FROM AUTHOR]

In this paper, a Van Koch printed antenna on a photonic-bandgap fractal substrate is presented. The substrate is designed with grounded Van Koch printed elements. The structure is a multifrequency radiator as a common fractal antenna, but the special synthesis of the substrate enhances the frequency bandwidth and gain, and drives the antenna to radiate a circularly polarized field. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 42: 397–402, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20316 [ABSTRACT FROM AUTHOR]

In this paper, the effects of the monopole antenna with windowed ground plane have been studied, including the impedance condition and the radiation patterns. A circularly microstrip monopole antenna is used as a radiated element. By utilizing a circular or rectangular slot of the extended ground plane to change the distribution of the electrical field, the injected power radiates from the slot and patch regions. According to the measured results, the radiation patterns and the antenna gain have been improved. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 42: 407–411, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20319 [ABSTRACT FROM AUTHOR]

In this paper, we study a rectangular microstripline-fed wide aperture-coupled microstrip antenna backed by a ground plane. In this case, a rectangular microstrip feed line and a wide slot lead to good impedance matching in a wide-frequency band. The 2.0 VSWR impedance bandwidth of the lower mode is 0.29 GHz (0.83–1.12 GHz, 32.2% at the center frequency of 0.9 GHz) and covers the cellular and GSM bands; the band of the upper mode reaches 0.93 GHz (1.69–2.62 GHz, 46.5% at the center frequency of 2.0 GHz) and covers the PCS, IMT-2000, WLL, and UMTS bands, in respectively. The results obtained for VSWR exhibit multiband characteristic. The peak antenna gain is 7.6 and 10.5 dBi for the lower (Cellular, GSM) and upper (DCS, PCS, IMT-2000, WLL) operations, respectively. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 42: 37–40, 2004; Published online Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20199 [ABSTRACT FROM AUTHOR]

A suspended microstripline-fed linear tapered slot antenna element and its E-plane linear arrays are presented in this paper. The element is studied and designed using the finite-difference time-domain (FDTD) method. The simulated results show that the element has a good antenna performance from 17 to 24 GHz. To build the E-plane arrays, a unique five-piece assembled structure which guarantees a uniform air-filled thin substrate in the suspended microstrip line parallel feed-network, has been developed. Four E-plane arrays with different numbers of elements (4, 8, 16, and 32) are fabricated and their antenna gains and patterns are examined experimentally. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 41: 451–455, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20168 [ABSTRACT FROM AUTHOR]

In this paper, we propose a new dual-band antenna for applications of the ISM band. The proposed antenna is designed to operate at 2.4 and 5.8 GHz. The lower-frequency band (2.4 GHz) can be obtained by using the meandering technique, and the upper-frequency band (5.8 GHz) for dual-band operation was achieved by embedding a backed microstrip line. Details of the proposed antenna design and experimental results are presented and discussed. The measured radiation patterns at 2.4 and 5.8 GHz and antenna gain across the respective frequency bands are also presented. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 41: 457–460, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20170 [ABSTRACT FROM AUTHOR]

In this paper, a microstrip network of the feeding module used in diverse applications of an antenna for dual-band wireless local-area network (WLAN) operation is designed, fabricated, and measured. A wideband Wilkinson power divider with the defected-ground structure (DGS) is integrated with a dual-band SPDT switch module in order to provide two individual signal paths for the input of a two-element antenna array. Two DGS slots are etched on the ground plane in order to reduce the loss of chip resistors, improve the impedance bandwidth, and enhance the efficiency of the output power. According to the simulated and measured results, the feeding module can be operated at the 2.4- and 5.2-GHz bands. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 41: 473–477, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20176 [ABSTRACT FROM AUTHOR]

The attenuation and slow-wave characteristics in an inverted embedded metal-insulator-semiconductor (IEM-MIS) microstrip line are investigated in this paper, based on the extracted frequency-dependent distributed parameters, that is, per-unit-length series resistance and inductance, shunt capacitance, and conductance of the structure. Parametric studies are performed to show the combined effects of different parameters, such as strip thickness, width, conductivity, embedding depth, and silicon conductivity and its thickness, on the mode attenuation constant and slow-wave factor (SWF). © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 41: 366–369, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20143 [ABSTRACT FROM AUTHOR]

In this paper, a microstrip filter has been designed, fabricated, and measured for application in ultra-wideband antennas. By using the combination of a band-stop filter and a low-pass filter, the band-selective characteristics can be demonstrated. In order to enhance the suppression of the out-of-band signals, a defected ground structure (DGS) with stopband performance is used. The passband responses of the filter, which range below 2.8 GHz and from 5.0 to 6.0 GHz, cover most commercial wireless communication systems. The LC-lumped equivalent circuit of the filter has been extracted and simulated by using transmission-line analysis. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 41: 248–251, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20107 [ABSTRACT FROM AUTHOR]

The traditional microstrip or coplanar-waveguide filter design restricts filter structure to regular shapes so that the results may not be optimal. In this paper, we present a novel design approach that allows arbitrary planar structures. This approach combines two powerful and flexible methods: the finite-element method (FEM) as the three-dimensional (3D) field simulator and the genetic algorithm (GA) as the optimization engine. In order to reduce the optimization time, parallel computing is also utilized. The FEM-GA design approach is much more flexible than traditional ones. Numerical examples are presented to show the validity and effectiveness of this approach. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 41: 276–279, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20116 [ABSTRACT FROM AUTHOR]

This paper presents a new fundamental single-balanced ring mixer incorporating T-shaped compact microstrip resonant cells (TS-CMRCs). The measured minimum single side-band (SSB) down-conversion loss of 3.3 dB is achieved for a 10.4-GHz RF signal and is better than 6 dB from 9.6–11.5 GHz with a 0.1-GHz IF. In addition, our working prototype demonstrates an excellent linearity response, in which the third-order intercept point (IP3) is 17 dBm with a spurious free-dynamic range of more than 55 dB. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 41: 206–209, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20095 [ABSTRACT FROM AUTHOR]

A novel compact slotted microstrip antenna for circular polarization (CP), using a new type of organic magnetic substrate for the first time, is proposed in this paper. The proposed antenna is analyzed using the FDTD method and demonstrated by experiment. The measured results of proposed CP square and circular patches show that this new magnetic substrate design not only reduces the antenna's size, but also provides much wider impedance and CP bandwidth. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 40: 497–500, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20014 [ABSTRACT FROM AUTHOR]

This paper deals with the 3D modeling of the photo-induced load created by a laser that illuminates a semiconductor substrate. This independent optical command allows us to change the microwave behavior of the microstrip device. We present a 3D-equivalent microwave model for the photo-injection in terms of equivalent conductivity plasma. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 40: 356–359, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.11380 [ABSTRACT FROM AUTHOR]

The mutual coupling between rectangular microstrip patches mounted on a spherical structure is studied in this paper. The analysis approach is based on the spectral-domain method of moments (MoM). An approximate method is developed to calculate coupling between currents located on different patches. A laboratory model is built to test different configurations of patches and to validate the calculated results. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 40: 387–391, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.11389 [ABSTRACT FROM AUTHOR]

Directly applying the higher-order FDTD method to the computation of antenna patterns has not been a practical approach thus far. One of the main difficulties is how to handle the perfect electric conductor (PEC), which is always present. This paper describes a procedure for handling the PEC using the S24 FDTD method, which is capable of directly computing the antenna far-field patterns. Accuracy of the algorithm is demonstrated by comparing the antenna patterns with those calculated from the near-to-far field transformation and cavity model. [ABSTRACT FROM AUTHOR]

This paper describes the thin-film fabrication process and the performance of 60-GHz aperture-coupled microstrip patch antennas printed on fused quartz substrates. It is shown that their characteristics (input impedance, axial ratio) are strongly modified by residual air gaps located between the two substrates of the antenna. In particular, FDTD simulations demonstrate that these parasitic effects can be minimized by using two ground/reflecting planes and by keeping the thickness of the air layer thinner than λ0/250, where λ0 is the free-space wavelength. To face this technological problem, two intermediate metal and adhesive (low-temperature) wafer bonding techniques, respectively based on indium and polymer layers, have been developed and validated experimentally for linear and circular polarization patch antennas and arrays. The lift-off fabrication process is also described. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 40: 41–47, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.11281 [ABSTRACT FROM AUTHOR]

In this paper, we present a uniplanar strip-dipole antenna and a bow-tie antenna fed by a coplanar waveguide (CPW) that both use a wideband and compact balun. The balun, which consists of planar lumped-LC circuits, affects the transition from an unbalanced CPW to a balanced coplanar strip. The antennas are designed to operate at the 2.44-GHz ISM-band. The measured data show that such broadband balun-based antennas enjoy the advantages of broad bandwidth and extra compactness. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 40: 70–73, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.11287 [ABSTRACT FROM AUTHOR]

This paper presents a novel approach for the efficient solution of a class of microstrip antennas using the newly introduced characteristic basis functions (CBFs) in conjunction with the method of moments (MoM). The CBFs are special types of high-level basis functions, defined over domains that encompass a relatively large number of conventional subdomain basis functions, for example, triangular patches or rooftops. The advantages of applying the CBF method (CBFM) are illustrated by several representative examples, and the accuracy as well as the computation time are compared to those of conventional direct computation. It is demonstrated that the use of CBFs can result in significant savings in computation time, with little or no compromise in the accuracy of the solution. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 39: 456–464, 2003 [ABSTRACT FROM AUTHOR]

In this paper, bow-tie microstrip antennas (BMAs) conformal to cylinders with small radii are studied. One-element BMA and two-element BMA arrays, conformal to cylinders with small radii and finite length, are simulated and measured. Theoretical results are compared with experimental ones, showing good agreement. It is observed that not only radiation patterns are changed, but also the resonant frequency is lowered and the impedance bandwidth is reduced significantly when the cylinder's radius is decreased. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 39: 511–514, 2003 [ABSTRACT FROM AUTHOR]

This paper presents the design and development of a compact dual linearly polarized aperture-coupled microstrip patch antenna array system for radio frequency identifications (RFID) applications. Two different antenna designs, Antenna-1 and Antenna-2, for RFID tag and reader applications are presented at the C and S bands, respectively. The antennas use two symmetric coupling apertures to excite two orthogonal modes for dual-polarization operation. High isolation of the order of -35 dB is obtained by proper selection of the shape and positions of the coupling aperture. The prototype antenna yields a 14.6-dBi peak gain, a 36° 3-dB beamwidth (HPBW), a 30-dB cross-polarization level, and isolation better than 38 dB between the two orthogonal polarizations (Tx and Rx) at the S band, and a 7.7-dBi peak gain, a 70° 3-dB beamwidth (HPBW), a 24-dB cross-polarization level, and isolation better than 38 dB between the orthogonal polarization at the C-band, respectively. The antenna yields a 10-m identification-read range in the field trial. The findings are very promising for RFID applications. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 39: 354–360, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.11215 [ABSTRACT FROM AUTHOR]

This paper presents new and simple models based on artificial neural networks (ANNs) to determine the effective permittivities of suspended microstrip (SM) and inverted microstrip (IM) lines. The neural results are in very good agreement with the theoretical and experimental results available in the literature for both SM and IM lines. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 39: 383–389, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.11225 [ABSTRACT FROM AUTHOR]

In this paper, a novel uniplanar compact EBG structure—a dumbbell structure—is used in the design of a 2 × 2 microstrip antenna array, which has a resonant frequency of 5.6 GHz. Due to the suppression of the surface wave introduced by the EBG structure, the E-plane mutual coupling between the array elements is reduced, as well as the side-lobe level in the E-plane radiation pattern. Moreover, a 1.5-dB increase in the gain of the main lobe is observed. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 39: 395–399, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.11228 [ABSTRACT FROM AUTHOR]

This paper describes an efficient design method for an aperture-coupled microstrip patch antenna, based on an improved transmission line model. The governing equations have been derived and applied to the design of the antenna with a center operating frequency of 11 GHz. The theoretical return loss was compared to the observed results from the fabricated antenna. The error of the proposed design method is less than 1.5%. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 39: 75–78, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.11132 [ABSTRACT FROM AUTHOR]

Dual-band stacked microstrip patch antennas are a popular choice for wireless and other vehicular communication applications. They are also being considered for use in feed arrays for reflector antennas. In this paper, novel center-feeding schemes to achieve the desired dual-band response will be presented. Also, novel side-feeding schemes for a potential application in arrays have been investigated. L-band frequencies were chosen to test the concept. For the stacked patch configuration, the primary objective was to get the antenna to resonate at two frequencies—1.575 GHz for the upper patch and 1.228 GHz for the lower patch—with a shared aperture and two independent excitations. Return-loss, isolation, and pattern measurements for several antenna prototypes are presented. The measured results are compared with the simulation results from an FDTD code developed at UCLA. Extension of the concept for dual-polarization and array configurations has been explored. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 38: 467–475, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.11092 [ABSTRACT FROM AUTHOR]