Showing papers in "International Journal of Rf and Microwave Computer-aided Engineering in 2004"
TL;DR: In this article, a new method based on the differential evolution (DE) algorithm is proposed for antenna-array pattern synthesis with prescribed nulls, where the array excitation amplitudes are the only controlling parameters, and the objectives are to synthesize array patterns with nulls imposed on directions of interference while keeping the sidelobe levels (SLLs) below prescribed levels.
Abstract: A new method based on the differential evolution (DE) algorithm is proposed for antenna-array pattern synthesis with prescribed nulls. The array excitation amplitudes are the only controlling parameters, and the objectives are to synthesize array patterns with nulls imposed on directions of interferences while keeping the sidelobe levels (SLLs) below prescribed levels. Many factors such as the excitation dynamic range ratio, null depth level, null width, and SLLs are taken into account in the synthesis. Simulation results of several typical problems are compared with published results to illustrate the effectiveness of the proposed method. © 2003 Wiley Periodicals, Inc. Int J RF and Microwave CAE 14: 57–63, 2004.
115 citations
TL;DR: In this article, a reconfigurable matching network based on the loaded-line technique was proposed for power amplifiers at 4-18 GHz and load-pull measurements at 10-28 GHz.
Abstract: We have developed a novel reconfigurable matching network based on the loaded-line technique. The network is composed of N-switched capacitors (N = 4–8) with a capacitance ratio of 4–5:1 and is suitable for power amplifiers at 4–18 GHz, or as an impedance tuner for noise parameter and load-pull measurements at 10–28 GHz. The networks are very small, and offer better performance than double or triple stub matching networks. Extensive loss analysis indicates that the 8-element network has a loss of 0.5 dB at 4–12 GHz, and less than 1.5 dB at 18 GHz, even when matching a 10Ω output impedance to a 50Ω load. As expected, the 4-element matching network has about half the loss of the 8-element network, but with much less impedance coverage. Both networks were simulated and measured in high VSWR conditions and can handle at least 500 mW of RF power at 4–18 GHz. The application areas are in phased array antennas, reconfigurable power amplifiers, and wideband noise-parameter and load-pull measurement systems. © 2004 Wiley Periodicals, Inc. Int J RF and Microwave CAE 14: 356–372, 2004.
79 citations
TL;DR: The method, based on the intersection‐approach concept, provides the phase distribution of the reflected field that best suits the required gain‐pattern specifications.
Abstract: This article presents an efficient phase-only synthesis method applied to contoured-beam reflectarrays. The method, based on the intersection-approach concept, provides the phase distribution of the reflected field that best suits the required gain-pattern specifications. In order to avoid undesired local minima, several successive stages, in which the tapering on the reflectarray's edge is gradually increased, are carried out to reach a final suitable result. As an example of its capabilities, the coverage of Europe is successfully synthesized. © 2004 Wiley Periodicals, Inc. Int J RF and Microwave CAE 14, 415–423, 2004.
68 citations
TL;DR: A novel reconfigurable matching network based on the loaded-line technique that is suitable for power amplifiers at 4–18 GHz, or as an impedance tuner for noise parameter and load-pull measurements at 10–28 GHz is developed.
Abstract: We have developed a novel reconfigurable matching network based on the loaded-line technique. The network is composed of N-switched capacitors (N 4–8) with a capacitance ratio of 4–5:1 and is suitable for power amplifiers at 4–18 GHz, or as an impedance tuner for noise parameter and load-pull measurements at 10–28 GHz. The networks are very small, and offer better performance than double or triple stub matching networks. Extensive loss analysis indicates that the 8-element network has a loss of 0.5 dB at 4–12 GHz, and less than 1.5 dB at 18 GHz, even when matching a 10 output impedance to a 50 load. As expected, the 4-element matching network has about half the loss of the 8-element network, but with much less impedance coverage. Both networks were simulated and measured in high VSWR conditions and can handle at least 500 mW of RF power at 4–18 GHz. The application areas are in phased array antennas, reconfigurable power amplifiers, and wideband noise-parameter and load-pull measurement systems. © 2004 Wiley Periodicals, Inc. Int J RF and Microwave CAE 14: 356–372, 2004.
37 citations
TL;DR: In this article, an efficient and systematic strategy to find the propagation constants of real, complex, and leaky modes of covered and uncovered planar multilayered isotropic/uniaxial waveguides is presented.
Abstract: An efficient and systematic strategy to find the propagation constants of real, complex, and leaky modes of covered and uncovered planar multilayered isotropic/uniaxial waveguides is presented. This strategy first builds up a pole-free characteristic function and then makes use of a root-searching scheme based on an integral nature method to search for its zeros. For uncovered waveguides, the branch points of the characteristic function can be removed by introducing the upper half-space vertical wavenumber as the working variable. Examples of the efficiency, reliability, and robustness of the presented technique are given for both covered and uncovered waveguides, which sets up this technique as a very convenient CAD tool. The method is also applied to study a new and interesting problem: the evolution of the modes of a grounded dielectric waveguide when increasing the permittivity of the upper semi-infinite medium. © 2003 Wiley Periodicals, Inc. Int J RF and Microwave CAE 14, 73–83, 2004
35 citations
TL;DR: In this article, the parallel-circuit Class E tuned power amplifiers with load networks consisting of either one capacitance and one inductor or a parallel LC circuit and series filter are described and analyzed.
Abstract: The parallel-circuit Class E tuned power amplifiers with load networks consisting of either one capacitance and one inductor or a parallel LC circuit and series filter are described and analyzed. The elements of the load networks are defined using the same analytical approach with a set of the exact design equations. The ideal collector voltage and current waveforms for both configurations demonstrate a possible 100% efficiency and do not overlap. RF and microwave applications are demonstrated based on the simulation and experimental results of low-voltage InGaP/GaAs HBT and high-voltage LDMOSFET power amplifiers. These switched-mode parallel-circuit Class E power amplifiers offer a new challenge for RF and microwave power amplification by providing high-efficiency operating conditions. © 2003 Wiley Periodicals, Inc. Int J RF and Microwave CAE 14, 21–35, 2004.
33 citations
TL;DR: In this paper, an electrostatically actuated broadband ohmic microswitch was developed for RF and microwave applications, which is a three-terminal device based on a cantilever beam and is fabricated using an all-metal, surface-micromachining process.
Abstract: An electrostatically actuated broadband ohmic microswitch has been developed for RF and microwave applications. The switch is a three-terminal device based on a cantilever beam and is fabricated using an all-metal, surface-micromachining process. It operates in a hermetic environment obtained through a glass frit wafer-bonding process. RF lifetimes greater than 1010 cycles have been achieved for the wafer capped switch. Typical insertion loss and isolation for a 2-contact switch at 10 GHz are 0.4 and 20 dB, respectively, while the 8-contact switch yields an insertion loss and isolation of 0.2 dB and 27 dB at 2 GHz, respectively. © 2004 Wiley Periodicals, Inc. Int J RF and Microwave CAE 14: 338–344, 2004.
29 citations
TL;DR: A hybrid-learning algorithm, which combines the least-square method and the backpropagation algorithm, is used to identify the parameters of ANFIS.
Abstract: A new method based on the adaptive neuro-fuzzy inference system (ANFIS) for calculating the resonant frequency of the equilateral triangular microstrip patch antenna is presented. The ANFIS has the advantages of the expert knowledge of the fuzzy inference system and the learning capability of neural networks. A hybrid-learning algorithm, which combines the least-square method and the backpropagation algorithm, is used to identify the parameters of ANFIS. The results of the new method show better agreement with the experimental results, as compared to the results of previous methods available in the literature. © 2004 Wiley Periodicals, Inc. Int J RF and Microwave CAE 14, 134–143, 2004.
28 citations
TL;DR: In this paper, a reconfigurable bandstop filter operating at 8, 10, 13, and 15 GHz that utilizes RF MEMS switches has been developed on high-resisitivity silicon substrate.
Abstract: A monolithic, low-power reconfigurable bandstop filter operating at 8, 10, 13, and 15 GHz that utilizes RF MEMS switches has been developed on high-resisitivity silicon substrate. The filter is based on microstrip transmission lines with radial stubs that provide different reactance at different resonant frequencies. Selection of the desired stub reactance is achieved with cantilever capacitive RF MEMS switches that are electrostatically actuated. The tuning range of the fabricated filter is 7 GHz (8–15 GHz), which is about 60p of the mid-band frequency. The rejection at the notch of the filter and the -10-dB bandwidth range from -20 dB to -27 dB and 5p to 9.7p, respectively, at the different resonant frequencies The pass-band insertion loss was found to be around 0.5 dB. © 2004 Wiley Periodicals, Inc. Int J RF and Microwave CAE 14: 373–382, 2004.
23 citations
TL;DR: In this paper, an electric field measurement system based on electro-optic sampling (EOS) is described, which is able to map near and far-field patterns of millimeter-wave radiated from antennas by scanning the electric-field sensor probe.
Abstract: This article describes an electric-field measurement system that is based on electro-optic sampling (EOS). This system is able to map near- and far-field patterns of millimeter waves radiated from antennas by scanning the electric-field sensor probe. With the bandwidth set to more than 150 GHz, it can detect an electric field of less than 1.0 V/m at 60 GHz. This electric field is about one-tenth the field limit detectable by conventional microwave EOS systems. A comparison of measured and calculated electric fields in both the frequency- and time-domains demonstrates the accuracy and usefulness of the system. © 2004 Wiley Periodicals, Inc. Int J RF and Microwave CAE 14: 290–297, 2004.
22 citations
TL;DR: In this article, the basic operation of a capacitive MEMS switch is described and two tools for examining device reliability, modeling, and on-chip experimentation, are discussed in the case of capacitive RF MEMS switches.
Abstract: Some applications of RF MEMS switches, such as aircraft condition monitoring and distributed satellite communication, present a unique challenge for device design and reliability. This article examines these switches when operational temperatures in the range -60°C to 100°C are envisioned. The basic operation of a capacitive MEMS switch is described and two tools for examining device reliability, modeling, and on-chip experimentation, are discussed in the case of capacitive MEMS switches. 1D, 2D, and 3D models are presented with emphasis on 3D coupled-field finite-element analysis, including temperature effects. Results and findings from the 3D simulations are reported. In particular, the advantages of employing corrugated membranes in the design of RF MEMS switches are assessed. Their performance in terms of reliability as a function of temperature is quantified. The effects of corrugation on the geometric parameters are discussed in the context of device-design optimization. In order to assess reliability experimentally, the M-test and the membrane deflection experiment (MDE) are reviewed due to their on-chip characteristic and simplicity. Ways in which these experimental/computational methodologies can be combined for identifying material properties and device performance is also highlighted. © 2004 Wiley Periodicals, Inc. Int J RF and Microwave CAE 14: 317–328, 2004.
TL;DR: Commonly used approaches for the design of power amplifiers (PAs), specifically in the microwave and millimeter‐wave frequency range, are reviewed and discussed.
Abstract: Commonly used approaches for the design of power amplifiers (PAs), specifically in the microwave and millimeter-wave frequency range, are reviewed and discussed. Measurement-based techniques are compared with CAD-based approaches, stressing their relative strengths and weaknesses. Simplified techniques are also discussed, particularly addressing the preliminary evaluation of the power capabilities of a given device and to gather physical insight into the power-generating mechanisms. Finally, harmonic tuning for high-efficiency power amplifier design is outlined, together with its basic application rules. © 2004 Wiley Periodicals, Inc. Int J RF and Microwave CAE 14: 493–506, 2004.
TL;DR: A dielectric resonator combining two cylindrical dielectrics of different material and height and excited by a coaxial probe is considered in this paper, where the effect of the antenna parameters, such as the ratio of the height and radius of the Dielectric Resonator and the probe length, are investigated.
Abstract: A dielectric resonator combining two cylindrical dielectrics of different material and height and excited by a coaxial probe is considered. The effect of the antenna parameters, such as the ratio of the height and radius of the dielectrics and the effect of the probe length, are investigated. Analysis of the antenna is performed numerically using the method of moments (MoM) and verified by the finite-difference time-domain (FDTD) method. Agreement between the two methods is excellent. The performance of the antenna on a cellular-communication system is also considered. © 2004 Wiley Periodicals, Inc. Int J RF and Microwave CAE 14, 441–446, 2004.
TL;DR: In this article, a neural network with radial-basis functions (RBF-NN) is applied to microwave imaging of cylinders. But the method is limited to the case of two cylinders.
Abstract: In this article, a neural network with radial-basis functions (RBF-NN) is applied to microwave imaging of cylinders. Initially, the shape function of the target cylinder is expanded by a Fourier series. The RBF-NN is trained by some direct-scattering data sets and thus can predict the images of the target cylinders. © 2004 Wiley Periodicals, Inc. Int J RF and Microwave CAE 14, 398–403, 2004.
TL;DR: In this article, a novel approach for modeling radio-frequency microelectromechanical system (RF MEMS) resonators by using artificial neural network (ANN) modeling is presented.
Abstract: In this article, a novel and efficient approach for modeling radio-frequency microelectromechanical system (RF MEMS) resonators by using artificial neural network (ANN) modeling is presented. In the proposed methodology, the relationship between physical-input parameters and corresponding electrical-output parameters is obtained by combined circuit/full-wave/ANN modeling. More specifically, in order to predict the electrical responses from a resonator, an analytical representation of the electrical equivalent-network model (EENM) is developed from the well-known electromechanical analogs. Then, the reduced-order, nonlinear, dynamic macromodels from 3D finite-element method (FEM) simulations are generated to provide training, validating, and testing datasets for the ANN model. The developed ANN model provides an accurate prediction of an electrical response for various sets of driving parameters and it is suitable for integration with an RF/microwave circuit simulator. Although the proposed approach is demonstrated on a clamped-clamped (C-C) beam resonator, it can be readily adapted for the analysis of other micromechanical resonators. © 2004 Wiley Periodicals, Inc. Int J RF and Microwave CAE 14: 302–316, 2004.
TL;DR: In this paper, a new method based on the differential evolution (DE) algorithm is proposed for antenna-array pattern synthesis with prescribed nulls, where the array excitation amplitudes are the only controlling parameters, and the objectives are to synthesize array patterns with nulls imposed on directions of interference while keeping the sidelobe levels (SLLs) below prescribed levels.
Abstract: A new method based on the differential evolution (DE) algorithm is proposed for antenna-array pattern synthesis with prescribed nulls. The array excitation amplitudes are the only controlling parameters, and the objectives are to synthesize array patterns with nulls imposed on directions of interferences while keeping the sidelobe levels (SLLs) below prescribed levels. Many factors such as the excitation dynamic range ratio, null depth level, null width, and SLLs are taken into account in the synthesis. Simulation results of several typical problems are compared with published results to illustrate the effectiveness of the proposed method. © 2003 Wiley Periodicals, Inc. Int J RF and Microwave CAE 14: 57–63, 2004.
TL;DR: In this paper, the transmission characteristics of various fabricated square and circular on-chip transformers are studied and compared, and both self and mutual inductances are extracted accurately, which facilitates further study of the coupling coefficients and loss mechanism of the on chip transformers.
Abstract: The transmission characteristics of various fabricated square and circular on-chip transformers are studied and compared in this article. According to the proposed lumped-element equivalent-circuit model and the measured broadband S-parameters, both self and mutual inductances are extracted accurately, which facilitates further study of the coupling coefficients and loss mechanism of on-chip transformers. © 2004 Wiley Periodicals, Inc. Int J RF and Microwave CAE 14, 424–432, 2004.
TL;DR: In this paper, a statistical description of the global performance of on-chip spiral inductors, based on extensive measurement, is presented, where various local scalable formulas are obtained in order to describe the features of these inductors.
Abstract: A statistical description of the global performance of on-chip spiral inductors, based on extensive measurement is presented. These inductors were fabricated with different turn numbers or track lengths/track widths, but with the same spacing. From the S parameters measured using a de-embedding technique, the inductance L, Q factor, self-resonance frequency, and figure-of-merit indicator (FMI) of these inductors are determined. Various local scalable formulas are obtained in order to describe the features of these inductors. Based on extensive parametric studies, certain ways to improve these inductor performances can be found. © 2004 Wiley Periodicals, Inc. Int J RF and Microwave CAE 14, 111–121, 2004.
TL;DR: A modeling procedure which provides an accurate large-signal response for variation in bias, input power level, and fundamental frequency for FET/HEMT transistors is designed and illustrated by designing a nonlinear PHEMT model, which includes an accurate Large Signals input response and works with variations in the aforementioned input conditions.
Abstract: A modeling procedure which provides an accurate large-signal response for variation in bias, input power level, and fundamental frequency for FET/HEMT transistors is designed. A procedure for measuring the large-signal input response on an easily implemented system is presented. The technique is illustrated by designing a nonlinear PHEMT model, which includes an accurate large-signal input response and works with variations in the aforementioned input conditions. © 2004 Wiley Periodicals, Inc. Int J RF and Microwave CAE 14, 122–133, 2004.
TL;DR: In this article, the gain sensitivity of the T and Π types of distributed-parameter amplifiers with respect to the physical length l and characteristic impedance Z0 was analyzed.
Abstract: Enhancement of a gain-sensitivity analysis of electrical networks is presented by computing gain sensitivities with respect to network parameters. A simple and versatile method. The so-called chain-sensitivity matrix is presented and compared with the current method in the literature, gain factorization, for the gain sensitivities of the cascaded networks. Analytical formulas are derived to calculate gain sensitivities of the T and Π types of distributed-parameter amplifiers with respect to the physical length l and characteristic impedance Z0, rather than using a time-intensive computer-based perturbation method. The numerical results of the T- and Π-type amplifiers for the design targets of noise figure Freq = 0,46 dB ( 1, 12) input VSWR Vireq = 1, power gain GTreq = 12 dB ( 15, 86) and the bandwidth B = 2 GHz − 11 GHz are given in comparison to each other. © 2004 Wiley Periodicals, Inc. Int J RF and Microwave CAE 14: 462–474, 2004.
TL;DR: An efficient implementation of an iterative method that includes a fast‐mode transformation (FMT) that has the advantages of simplicity and not involving basis functions and inversion of matrices, as used in other calculation methods is presented.
Abstract: This article presents an efficient implementation of an iterative method that includes a fast-mode transformation (FMT). The method has the advantages of simplicity and not involving basis functions and inversion of matrices, as used in other calculation methods. Therefore, this approach has the potential to be capable of analysing larger bodies than other classical techniques. An implementation of the iterative calculation is shown for the extraction of S parameters of microwave components and antennas. The good agreement between the simulation results and experimental published data justifies the design procedure and validates the present analysis approach. © 2004 Wiley Periodicals, Inc. Int J RF and Microwave CAE 14, 404–414, 2004.
TL;DR: Simulations show that an adaptive predistortion scheme to compensate for the HPA's nonlinearity by combining adaptive structure‐varying neural networks and a fuzzy controller can very effectively prevent the warping of the signal constellations, thus reducing the system's BER and learning time.
Abstract: In digital radio systems, high data transmission rates require the use of spectrally efficient linear modulation techniques; however, these techniques are generally sensitive to nonlinearity caused by the high-power amplifier (HPA) employed in transmitter systems. The nonlinearity of HPA is potentially responsible for spectral spreading, adjacent channel interference (ACI), and degradation of bit-error rates (BERs). This article proposes an adaptive predistortion scheme to compensate for the HPA's nonlinearity by combining adaptive structure-varying neural networks and a fuzzy controller. Simulations show that this predistortion scheme can very effectively prevent the warping of the signal constellations, thus reducing the system's BER and learning time. © 2003 Wiley Periodicals, Inc. Int J RF and Microwave CAE 14: 15–20, 2004.
TL;DR: In this paper, the authors discussed the slope exponent that gives a minimum of variation in capacitance for the microwave excitation in the circuit in which diodes are connected in anti-series.
Abstract: A variable-capacitance (varactor) diode is widely applied in microwave devices, which utilize the characteristic property that the junction capacitance is varied by an externally applied voltage. In applications of capacitance-controlled devices, such as voltage-controlled oscillators, the capacitance is varied by the control-bias voltage, whereas the variation in capacitance for microwave RF-signal voltages should be minimized in order to suppress higher-order distortions in the output signal. The capacitance-voltage characteristic of a varactor diode is characterized by a slope exponent γ. This article discusses the slope exponent that gives a minimum of variation in capacitance for the microwave excitation in the circuit in which diodes are connected in anti-series. The analysis is based upon a time-domain-oriented method, in which we first obtain the voltage and current waveforms by solving differential equations with respect to time and then calculate the frequency-domain quantities by Fourier analysis of voltage and current waveforms. © 2004 Wiley Periodicals, Inc. Int J RF and Microwave CAE 14: 274–282, 2004.
TL;DR: In this paper, the opto-electrical interaction of a microwave device was characterized by combining a large-signal network analyzer setup with a modulated laser (1550-nm) module.
Abstract: This article shows how the opto-electrical interaction of a microwave device, that is, a metamorphic HEMT, can be characterized by combining a large-signal network analyzer setup with a modulated laser (1550-nm) module. Furthermore, an optically tunable oscillator has been realized in multilayer thin-film technology. © 2004 Wiley Periodicals, Inc. Int J RF and Microwave CAE 14: 535–542, 2004.
TL;DR: A dielectric resonator combining two cylindrical dielectrics of different material and height and excited by a coaxial probe is considered in this paper, where the effect of the antenna parameters, such as the ratio of the height and radius of the Dielectric Resonator and the probe length, are investigated.
Abstract: A dielectric resonator combining two cylindrical dielectrics of different material and height and excited by a coaxial probe is considered. The effect of the antenna parameters, such as the ratio of the height and radius of the dielectrics and the effect of the probe length, are investigated. Analysis of the antenna is performed numerically using the method of moments (MoM) and verified by the finite-difference time-domain (FDTD) method. Agreement between the two methods is excellent. The performance of the antenna on a cellular-communication system is also considered. © 2004 Wiley Periodicals, Inc. Int J RF and Microwave CAE 14, 441–446, 2004.
TL;DR: Three‐dimensional (3D) full‐wave analysis and design of bandpass frequency‐selective surfaces (FSSs) is presented andWave propagation through FSSs, which is otherwise difficult to quantify, can be visualised by using a commercial CAD tool.
Abstract: Three-dimensional (3D) full-wave analysis and design of bandpass frequency-selective surfaces (FSSs) is presented. By using the unique features of a unit cell and the periodic boundary conditions, infinite FSSs can be simulated. Wave propagation through FSSs, which is otherwise difficult to quantify, can be visualised by using a commercial CAD tool. The creation of the simulation model, interpretation and analysis of the outcome, and comparison with experimental results are presented for the square-slot and the square-loop-slot band-pass FSS. © 2004 Wiley Periodicals, Inc. Int J RF and Microwave CAE 14, 391–397, 2004.
TL;DR: In this paper, an accurate design database for the characteristic parameters of the microstrip line, namely, effective dielectric constant, characteristic impedance, and attenuation coefficient, has been generated using the spectral-domain method (SDM).
Abstract: Modelling of MMIC multidielectric microstrip line on GaAs substrate for its precise characterization has been presented in this article. An accurate design database for the characteristic parameters of the microstrip line, namely, effective dielectric constant, characteristic impedance, and attenuation coefficient, has been generated using the spectral-domain method (SDM). The accuracy of the developed database for the frequency range 1 to 40 GHz has been verified with the experimental results. On-wafer measurements have been carried out to minimize the parasitic losses at the high frequencies and the effect of CPW-pads has been de-embedded from the measured S-parameters to obtained accurate characteristic parameters of the microstrip line. The theoretical and the measured values of the characteristic parameters of microstrip lines show good agreement within 1% to 2%. This work is expected to be useful in GaAs foundries for accurate MMIC-CAD modelling of microstrip lines up to 40 GHz. © 2004 Wiley Periodicals, Inc. Int J RF and Microwave CAE 14, 475–482, 2004.
TL;DR: A versatile FDTD parallel computation system is developed by using Fortran90 and the MPI library that uses dynamic memory allocation, which provides a more versatile system and more efficient use of memory.
Abstract: Given the remarkable advances in supercomputers, large-scale electromagnetic-field analyses are becoming possible by FDTD parallel computation. In this study, a versatile FDTD parallel computation system is developed by using Fortran90 and the MPI library. The system uses dynamic memory allocation, which provides a more versatile system and more efficient use of memory. Using the system, we analyze, for the first time, the radiation characteristics of an antenna mounted on a realistic vehicle model. © 2004 Wiley Periodicals, Inc. Int J RF and Microwave CAE 14: 253–261, 2004.
TL;DR: An approach is developed to analyze microstrip antennas on finite chiral substrates using the finite‐element method (FEM), and the perfectly matched layers (PMLs) in the chiral media is employed.
Abstract: An approach is developed to analyze microstrip antennas on finite chiral substrates using the finite-element method (FEM). The perfectly matched layers (PMLs) in the chiral media is employed in this work. First, the characteristics of microstrip antennas on infinite conventional, ferrite, and chiral substrates are respectively analyzed in order to validate our analysis. Then microstrip antennas on finite chiral substrates are investigated as a comparison with those on infinite chiral substrates. Finally, the input impedances of microstrip antennas on infinite and finite chiral substrate are calculated. © 2003 Wiley Periodicals, Inc. Int J RF and Microwave CAE 14: 49–56, 2004.
TL;DR: In this paper, an empirical model with an external substrate network is proposed to simulate the RF nonlinear characteristics of a MOSFET accurately in the wide range of operating bias points.
Abstract: A new empirical model with an external substrate network is proposed to simulate the RF nonlinear characteristics of a MOSFET accurately in the wide range of operating bias points. An accurate drain current equation is developed to model the nonlinear transconductance characteristics of a RF MOSFET, and improved nonlinear capacitance equations are used. The values of modeled S21 parameters using the new drain current equation show much better agreement with measured ones than those using the conventional formula over the wide bias range, thus verifying the accuracy of the new model. © 2004 Wiley Periodicals, Inc. Int J RF and Microwave CAE 14, 182–189, 2004.