Showing papers in "International Journal of Rf and Microwave Computer-aided Engineering in 2008"
TL;DR: In this article, the particle swarm optimization algorithm is used to calculate the complex excitations, amplitudes and phases, of the adaptive circular array elements, and the performance of an adaptive array using 3-bit amplitude and 4-bit phase shifters is studied.
Abstract: In this article, the particle swarm optimization algorithm is used to calculate the complex excitations, amplitudes and phases, of the adaptive circular array elements. To illustrate the performance of this method for steering a signal in the desired direction and imposing nulls in the direction of interfering signals by controlling the complex excitation of each array element, two types of arrays are considered. A uniform circular array (UCA) and a planar uniform circular array (PUCA) with 16 elements of half-wave dipoles are examined. Also, the performance of an adaptive array using 3-bit amplitude and 4-bit phase shifters are studied. In our analysis, the method of moments is used to estimate the response of the dipole UCAs in a mutual coupling environment. © 2007 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2008.
61 citations
TL;DR: In this article, a general and easy procedure for designing the symmetrical Wilkinson power divider that achieves equal-power split at N arbitrary frequencies is introduced, where each quarter-wave branch in the conventional Wilkinson divider is replaced by N sections of transmission lines, and the isolation between the output ports is achieved by using N resistors.
Abstract: In this paper, a general and easy procedure for designing the symmetrical Wilkinson power divider that achieves equal-power split at N arbitrary frequencies is introduced. Each quarter-wave branch in the conventional Wilkinson divider is replaced by N sections of transmission lines, and the isolation between the output ports is achieved by using N resistors. The design parameters are the characteristic impedances and lengths of the N transmission line sections, and the N isolation resistors. The even–odd modes of analysis are used to derive the design equations. Closed-form expressions, which are suitable for CAD purposes, are derived for the dual-band divider. For N ≥ 3, closed-form expressions are not available, and therefore, the powerful particle swarm optimization method is used to obtain the design parameters. Examples of the dual-, triple-, and quad-band dividers are presented to validate the proposed design procedure, and the results are compared, wherever possible, with published results using other methods. © 2007 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2008.
50 citations
TL;DR: In this paper, the authors present a brief but thorough comparative study of analytical techniques developed for modeling different types of advanced microwave transistors: GaAs, GaN, and FinFETs.
Abstract: Although many successful techniques have been proposed in the last decades for extracting the small signal equivalent circuit for microwave transistors from scattering parameter measurements, small signal modeling is still object of intense research. Further improvement and development of the proposed methods are incessantly required to take into account the continuous and rapid evolution of the transistor technology. The purpose of this article is to facilitate the choice of the most appropriate strategy for each particular case. For that, we present a brief but thorough comparative study of analytical techniques developed for modeling different types of advanced microwave transistors: GaAs HEMTs, GaN HEMTs, and FinFETs. It will be shown that a crucial step for a successful modeling is to adapt accurately the small signal equivalent circuit topology under “cold” condition to each investigated technology. © 2008 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2008.
46 citations
TL;DR: In this article, a methodology to thoroughly characterize an electric near-field probe based on small dipole antenna is presented, both theoretical investigations and experimental direct measurements determine the various characteristics of the probe such as selectivity, sensitivity and spatial resolution.
Abstract: A methodology to thoroughly characterize an electric near-field probe based on small dipole antenna is presented. Both theoretical investigations and experimental direct measurements determine the various characteristics of the probe such as selectivity, sensitivity and spatial resolution. Results show the efficiency of the probe for diagnosing electromagnetic phenomena. © 2008 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2008.
38 citations
TL;DR: In this article, the response of RF microelectromechanical systems (RF MEMS), barium strontium titanate (BST), and gallium arsenide (GaAs)-based tunable filters and reconfigurable matching networks to a wideband code-division-multiple access signal cen- tered at 1.95 GHz is presented.
Abstract: This article presents the response of RF microelectromechanical systems (RF MEMS), barium strontium titanate (BST), and gallium arsenide (GaAs)-based tunable filters and reconfigurable matching networks to a wideband code-division-multiple-access signal cen- tered at 1.95 GHz. The RF MEMS tunable filter and impedance tuner result in very low inter- modulation distortion and spectral regrowth compared to their BST and GaAs counterparts. The linearity of the BST and GaAs tunable networks improves considerably by using a series combination of BST and GaAs varactors, but the RF MEMS-based networks still show the best linearity of all three technologies. Also, it is shown that the reconfigurable networks, tuned with capacitive RF MEMS can handle up to 1 W of RF power with no self-actuation. V C 2007
32 citations
TL;DR: A novel technique is developed to apply bacterial foraging optimization technique in conjunction with the expressions developed to calculate accurately the resonant frequency of rectangular microstrip antenna of any dimension and of any substrate thickness.
Abstract: Resonant frequency of rectangular microstrip antenna having various substrate thicknesses are generally calculated using the standard expressions presented in literatures But these equations suffer from errors when compared with the experimental values due to Quasi-TEM propagation in the microstrip structure and fringing field A number of researchers used soft computing approach such as neural networks and genetic algorithm on those equations to minimize the error for better accuracy Bacterial foraging, an evolutionary optimization technique conceived in recent times, has many advantages over genetic algorithm and is yet to be applied on the design of microstrip patch antenna In this article, a novel technique is developed to apply bacterial foraging optimization technique in conjunction with the expressions developed to calculate accurately the resonant frequency of rectangular microstrip antenna of any dimension and of any substrate thickness Further, bacterial foraging is applied to the calculatation of the feed point of microstrip antenna The technique developed in this article can be a generalized soft computing tool to calculate resonant frequency of rectangular microstrip antenna Similarly, the idea of the article can be used for calculating the various parameters of microstrip antennas of different structure and geometry © 2008 Wiley Periodicals, Inc Int J RF and Microwave CAE, 2008
29 citations
TL;DR: In this article, a nonlinear model of GaN-based electron devices is presented, which takes into account low-frequency dispersion due to self-heating and charge-trapping phenomena and provides accurate predictions at frequencies where nonquasi-static effects are important.
Abstract: A new empirical nonlinear model of GaN-based electron devices is presented in the article. The model takes into account low-frequency dispersion due to self-heating and charge-trapping phenomena and provides accurate predictions at frequencies where nonquasi-static effects are important. The model is based on the application of a recently proposed equivalent-voltage approach and is identified by using pulsed measurements of drain current characteristics and pulsed S-parameter sets. Full experimental validation on a GaN on SiC PHEMT is provided at both small- and large-signal operating conditions. © 2008 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2008.
26 citations
TL;DR: In this article, the theoretical analysis and engineering implementation of the planar substrate-integrated waveguide (SIW) ferrite junction circulator have been proposed, and the ferrite circulator has been applied to a planar SIW waveguide.
Abstract: The theoretical analysis and engineering implementation of the planar substrate-integrated waveguide (SIW) ferrite junction circulator have been proposed in this article. The ferrite junction circu...
24 citations
TL;DR: It can be concluded that the ANN may be replaced by the support vector machines in the regression applications because of its higher approximation capability and much faster convergence rate with the sparse solution technique.
Abstract: In this article, the support vector regression is adapted to the analysis and synthesis of microstrip lines on all isotropic-anisotropic dielectric materials, which is a novel technique based on the rigorous mathematical fundamentals and the most competitive technique to the popular artificial neural networks (ANN). In this design process, accuracy, computational efficiency and number of support vectors are investigated in detail and the support vector regression performance is compared with an ANN performance. It can be concluded that the ANN may be replaced by the support vector machines in the regression applications because of its higher approximation capability and much faster convergence rate with the sparse solution technique. Synthesis is achieved by utilizing the analysis black-box bidirectionally by reverse training. Furthermore, by using the adaptive step size, a much faster convergence rate is obtained in the reverse training. Besides, design of microstrip lines on the most commonly used isotropic-anisotropic dielectric materials are given as the worked examples. © 2008 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2008.
22 citations
TL;DR: This article presents an optimization immune algorithm (opt-IA) for null steering of linear antenna arrays by controlling only the element amplitudes and finds that the nulling technique is capable of steering the array nulls precisely to the undesired interference directions.
Abstract: This article presents an optimization immune algorithm (opt-IA) for null steering of linear antenna arrays by controlling only the element amplitudes. Nulling of the pattern is also achieved by controlling the phase-only and the complex weights (both the amplitude and phase) of the array elements. The opt-IA is a new evolutionary computing algorithm based on the clonal selection principle of immune system. To show the accuracy and flexibility of the proposed opt-IA, several examples of Chebyshev array pattern with the imposed single, multiple, and broad nulls are given. It is found that the nulling technique based on opt-IA is capable of steering the array nulls precisely to the undesired interference directions. © 2008 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2008.
22 citations
TL;DR: An implicit space mapping (ISM) method for microwave filter design that is enhanced and assisted by a tuning procedure that guides the parameter selections and enhances the performance of ISM optimization is demonstrated.
Abstract: We demonstrate an implicit space mapping (ISM) method for microwave filter design that is enhanced and assisted by a tuning procedure. This procedure helps us to select design variables as well as suitable preassigned parameters for an ISM implementation. It also aids us in the convergence of our ISM algorithm. We investigated and solved a microstrip notch filter using this technique. This shows that tuning-aided sensitivity analysis guides the parameter selections and enhances the performance of ISM optimization. © 2008 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2008.
TL;DR: This article describes a method of designing a reconfigurable dual-beam linear antenna array using bees algorithm, an optimization algorithm inspired by the behavior of the honey bees to find the optimal way of harvesting food resources around the hive.
Abstract: This article describes a method of designing a reconfigurable dual-beam linear antenna array using bees algorithm (BA). The BA is an optimization algorithm inspired by the behavior of the honey bees to find the optimal way of harvesting food resources around the hive. The proposed method is very simple and can be used directly in practice to synthesize multiple beam antenna arrays with digital attenuators and digital phase shifters. A good agreement between the desired pattern and the synthesized pattern using BA is obtained. © 2008 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2008.
TL;DR: In this paper, a Dual-Band Branch-Line coupler is presented, using short-circuited Composite Right/Left-Handed Transmission Lines as loading stubs, and Purely Right-Hand Artificial Transmission Lines.
Abstract: By using short-circuited Composite Right/Left-Handed Transmission Lines as loading stubs, and Purely Right-Handed Artificial Transmission Lines, a Dual-Band Branch-Line coupler is presented. The adoption of such technologies adds degrees of freedom with respect to other already proposed design techniques, thus allowing the development of a very compact device, and a larger flexibility in the choice of the two operating frequencies and corresponding bandwidths. © 2007 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2008.
TL;DR: In this paper, a linear array antenna design with desired radiation pattern has been presented based on genetic algorithm (GA) approach to solve complex antenna synthesis problems by suitably selecting the fitness function, even with a simple GA.
Abstract: A linear array antenna design with desired radiation pattern has been presented based on genetic algorithm (GA) approach. Examples of cosecant and flat-topped beam patterns are illustrated to show the flexibility of GA to solve complex antenna synthesis problems by suitably selecting the fitness function, even with a simple GA. The results have been validated by IE3D electromagnetic simulation. The antenna arrays with different element geometries can also be implemented using the proposed technique. © 2008 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2008.
TL;DR: In this paper, a ladder-lattice bulk acoustic wave (BAW) filter for W-CDMA reception front-ends (2.11-2.17 GHz) is presented.
Abstract: This article presents a study of ladder-lattice bulk acoustic wave (BAW) filters. First, a review of BAW technology and filters topologies is addressed. Next, a mixed ladder-lattice BAW filter for application on W-CDMA reception front-ends (2.11–2.17 GHz) is presented. An improved solidly mounted resonators (SMR) technology was used for the filter implementation. The filter synthesis methodology is briefly described. Layout guidelines are discussed enabling an optimized filter design. The filter on-wafer measurement results are as follows: -3.55 dB of insertion loss, -8.7 dB of return loss, an isolation higher than -47 dB at the transmission band (1.92–1.98 GHz) and an improved selectivity (-30 dB at 2.14 GHz ± 60 MHz). Therefore, we can observe that the mixed topology combines the advantages of ladder and lattice networks, having very steep responses and an improved isolation at undesired bands. © 2008 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2008.
TL;DR: In this article, the optimal design parameters of pyramid cone absorbers via genetic algorithm for the normal and oblique incidence of plane wave were investigated in one-dimensional inhomogeneous media.
Abstract: Array of absorbing pyramid cones are widely used in anechoic chambers. When the period of the array is small compared with wavelength, which is in the low-frequency limit; the plane wave reflection problem is simplified and can be studied in one-dimensionally inhomogeneous media. This article deals with the optimal design parameters of pyramid cone absorbers via genetic algorithm for the normal and oblique incidence of plane wave. The optimization parameters are the dielectric permittivity and the length of the absorber over a wide frequency band and incidence angle range. The cost function of the optimization algorithm is the reflection coefficient of the absorber which is to be minimized. The algorithm is applied to different frequency bands and incidence angles. The results show that the minimized reflection coefficients and corresponding relative permittivities and absorber lengths are acceptable for each application. © 2008 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2008.
TL;DR: An automated RNN modeling technique is proposed to efficiently determine the training waveform distribution and internal RNN structure during the offline training process, which extends a recent automatic model generation (AMG) algorithm from frequency-domain model generation to dynamic time- domain model generation.
Abstract: In this article, a recurrent neural network (RNN) method is employed for dynamic time-domain modeling of both linear and nonlinear microwave circuits. An automated RNN modeling technique is proposed to efficiently determine the training waveform distribution and internal RNN structure during the offline training process. This technique extends a recent automatic model generation (AMG) algorithm from frequency-domain model generation to dynamic time-domain model generation. Two types of applications of the algorithm are presented, transient electromagnetic (EM) behavior modeling of microwave structures, and time-domain envelope modeling of power amplifiers (PA). For transient EM modeling, we consider EM structures with varying material and geometrical parameters. AMG automatically varies the EM structural parameters during training and drives time-domain EM simulators to generate necessary amount of data for RNN to learn. AMG aims to model the transient behavior with minimum RNN order while satisfying accuracy requirements. In modeling PA behavior, an envelope formulation is used to specifically learn the AM-AM and AM-PM distortions due to third-generation (3G) digital modulation input. The RNN PA model is able to model these time domain distortions after training and can accurately model the amplifier behavior in both time (AM-AM, AM-PM) and frequency (spectral re-growth). © 2008 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2008.
TL;DR: In this article, a rigorous design procedure is carried out for a microwave amplifier by employing the Feasible Design Space and simple analytical gain gradients of the matching circuits, where the physical lengths and characteristic impedances of the transmission lines used in the matching circuit are chosen as the design variables and their lower and upper limits are bounded by the limits of the planar transmission line technology so that resulted microwave amplifier can be realized by this technology.
Abstract: In this article, a rigorous design procedure is carried out for a microwave amplifier by employing the Feasible Design Space and simple analytical gain gradients of the matching circuits. Physical lengths and characteristic impedances of the transmission lines used in the matching circuits are chosen as the design variables and their lower and upper limits are bounded by the limits of the planar transmission line technology so that resulted microwave amplifier can be realized by this technology. Feasible Design Target Space is determined by the compatible performance [noise (F), input VSWR (Vi), gain (GT)] triplets and their source ZS(ωi) and load ZL(ωi) terminations resulted from the performance characterization of the active device. These triplets take into account the physical limitations of the device and realization conditions so that Freq ≥ Fmin, Vireq ≥ 1, GT min ≤ GT req ≤ GT max; and ZS(ωi) and ZL(ωi) terminations be taken place within the “Unconditionally Stable Working Area”. Design of the amplifier for the compatible performance triplets is reduced to the design of the ZS(ωi) and ZL(ωi), i = 1…N terminations, which is achieved by the gain optimization of the two passive, reciprocal matching two-ports using the Darlington theorem. Analytical expressions of the gain gradients of the matching circuits are obtained by the two different methods: (i) chain sensitivity matrix approach; (ii) adjoint network approach. Gain gradients of the L-, T-, and Π-types of distributed-parameter matching circuits are obtained as worked examples. Then typical design examples are given with together the synthesized, target, simulated characteristics. © 2008 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2008.
TL;DR: Jokovic et al. as discussed by the authors presented a procedure for the detection of resonant frequencies in a cylindrical metallic cavity, based on transmission characteristic, and an analysis of procedure efficiency to resonant modes identification is conducted numerically and experimentally verified.
Abstract: The procedure for the resonant frequencies detection in a cylindrical metallic cavity, based on transmission characteristic, is presented in this article. An analysis of procedure efficiency to resonant modes identification is conducted numerically and experimentally verified. As a numerical tool, TLM time-domain method, enhanced with the wire compact model to account for the presence of feeding and monitoring probes, is used. Also, in terms of modes identification and resonant frequency dependence of probe length, results of transmission procedure are compared with corresponding previously published results of reflection procedure [J. Jokovic, B. Milovanovic, and N. Doncov, Int J RF Microwave CAE 16: 346–354, 2006.]. © 2008 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2008.
TL;DR: A method based on multiple adaptive-network-based fuzzy inference system (MANFIS) is presented for the synthesis of electrically thin and thick rectangular microstrip antennas (MSAs) in close agreement with the experimental results available in the literature.
Abstract: A method based on multiple adaptive-network-based fuzzy inference system (MANFIS) is presented for the synthesis of electrically thin and thick rectangular microstrip antennas (MSAs). MANFIS is an extension of a single-output adaptive-network-based fuzzy inference system to produce multiple outputs. Six optimization algorithms, least-squares, nelder-mead, genetic, hybrid learning, differential evolution and particle swarm, are used to identify the parameters of MANFIS. The synthesis results of MANFIS are in very good agreement with the experimental results available in the literature. When the performances of MANFIS models are compared with each other, the best result is obtained from the MANFIS model optimized by the least-squares algorithm. © 2008 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2008.
TL;DR: Simple and accurate closed-form formulas obtained by using a differential evolution algorithm are presented for the synthesis of coplanar waveguides (CPW) and are found to be better than 0.75%.
Abstract: Simple and accurate closed-form formulas obtained by using a differential evolution algorithm are presented for the synthesis of coplanar waveguides (CPW). The results of the synthesis formulas proposed in this article are compared with those of the quasi-static analysis, the synthesis formulas reported by the other researchers and also the experimental works available in the literature. The accuracy of the proposed synthesis formulas is found to be better than 0.75% for 9256 CPWs samples. © 2008 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2008.
TL;DR: In this paper, the shift-and-invert (SI) Arnoldi method is used to directly resolve the nonsymmetrical generalized eigenvalue problem, and the accuracy of FDFD algorithm is improved.
Abstract: The slow wave effect can be obtained by a capacitively loaded structure with a symmetrical interdigital line connected on both sides of the coplanar waveguide (CPW) central line. The ferroelectric thin film with high dielectric constant can reduce the size of circuit and make it possible to realize tunable devices such as filter by applying voltage on it. Actually, this kind of slow wave structure is a periodic guided-wave structure and can be analyzed by using classic finite difference frequency domain (FDFD) method for periodic guided-wave structures. However, the very compact slow-wave structures will usually result in simulation errors when the classic FDFD method is adopted, which will lead to a nonsymmetrical generalized eigenvalue problem. In this article, the shift-and-invert (SI) Arnoldi method is used to directly resolve this nonsymmetrical generalized eigenvalue problem. As a result, the accuracy of FDFD algorithm is improved. Especially for the large scale eigenvalue problem, SI method can also have a very fast speed of calculation. By means of its complex propagation constant obtained from simulation, one can extract circuit parameters of the interdigital capacitor. Consequently, one can analyze and design relevant resonators and filters in a quick and accurate manner, which are constructed with such interdigital slow wave structures. © 2008 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2008.
TL;DR: In this article, the authors proposed a microstrip dual-band bandpass filter that uses parallel-connected open-loop ring resonators and derived the input and output matches of resonators to the external feed lines using a simple transmission line theory.
Abstract: This article proposes a microstrip dual-band bandpass filter that uses parallel-connected open-loop ring resonators. Compared to many microstrip dual-band filters, the advantages of using microstrip open-loop ring resonators are easy calculation (half-guided-wavelength), easy fabrication (equal width for all 50-Ω lines and without grounding holes), and direct connection to external feed lines (reducing insertion loss caused by gap couplings). Another advantage of the filter is an asymmetrical feed on the ring resonator that provides sharp rejections at its adjacent bands. The input and output matches of resonators to the external feed lines are derived using a simple transmission-line theory. The results of the derivation provide a simple design rule for filter designers. Simulated and measured results are presented with good agreement. The filter has minimum insertion loss of 1.25 dB at 1.85 GHz and 1.6 dB at 2.33 GHz. The 3-dB fractional bandwidths are 5.9% for the 1.9-GHz bandpass filter and 4.7% for the 2.4-GHz bandpass filter, respectively. © 2008 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2008.
TL;DR: In this paper, a novel substrate integrated waveguide equivalent inductive-post filter is presented and optimally designed by HFSS and equivalent circuit method, which is fabricated with a standard low cost PCB process.
Abstract: A novel substrate integrated waveguide equivalent inductive-post filter is presented and optimally designed by HFSS and equivalent circuit method. The filter is fabricated with a standard low cost PCB process. Measured data are in agreement with the simulated results. Excellent performance in selectivity, out of band rejection and passband insertion loss are shown. © 2008 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2008.
TL;DR: In this article, a rigorous mode-matching technique has been developed to obtain the generalized admittance matrix of the Boifot junction, and the other elements of the device are also analyzed by mode matching.
Abstract: The full-wave design of broadband ortho-mode transducers based on the Boifot junction has two main aspects: an efficient analysis method and a design process divided into tasks with relatively low computational effort. In the analysis part, a rigorous mode-matching technique has been developed to obtain the generalized admittance matrix of the Boifot junction. The other elements of the device are also analyzed by mode-matching. With respect to the design, the proposed procedure starts with the optimization of the individual building blocks of the device. Their interaction is also taken into account in a systematic process. The analysis and design methods have been validated with other numerical methods and an experimental prototype. © 2008 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2008.
TL;DR: In this article, a high-gain dual-band antenna for the wireless local area network system is presented, where two symmetrical linear arrays can be dynamically reconfigured that could switch radiation pattern with a switchable feed circuit between direction and omnidirection.
Abstract: A high-gain dual-band antenna for the wireless local area network system is presented in this article. Two symmetrical linear arrays can be dynamically reconfigured that could switch radiation pattern with a switchable feed circuit between direction and omnidirection. The antenna can also be used for a pattern diversity antenna for the multiple-input–multiple-output communication systems. The design process for the antenna system is given, and the parameters and characteristics of the antennas are achieved by the method. Measured return losses, isolation, and radiation patterns are in good agreement with the simulated ones, which illustrates that the method is valid and the antenna system can be integrated with pattern reconfigurable and pattern diversity applications. © 2008 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2008.
TL;DR: In this paper, the design, fabrication, and testing of a wide band single-ended power amplifier (PA) using GaN field effect transistors (FETs) are reported.
Abstract: In this article, the design, fabrication, and testing of a wide band single-ended power amplifier (PA) using GaN field effect transistors (FETs) are reported. The single-ended amplifier demonstrates a bandwidth larger than 30% around 2 GHz, with a high gain, PAE, and output power combination. © 2008 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2008.