Analysis Of Microwave Circuits Research Articles

An efficient multilayered shielded microwave circuit analysis method based on neural networks

An efficient multilayered shielded microwave circuit analysis method based on neural networks

Stability Analysis of Nonlinear Circuits Driven With Modulated Signals

Existing methods for the large-signal stability analysis of microwave circuits assume a periodic excitation, usually consisting of a single tone. However, practical circuits such as power amplifiers will generally be driven by modulated signals or multiple input tones. This paper presents a procedure for the stability analysis of linear time-varying systems, applicable to circuits excited with nonperiodic input signals. The procedure is based on the determination of the time-varying poles associated to an input-output representation of the system. Under modulated signals, this representation is obtained by linearizing the envelope-transient system that rules the circuit behavior. The formulation and methodology have been applied to a simple nonlinear circuit with arbitrary excitation and a practical power-combined amplifier at 3 GHz with very good agreement in comparison with independent simulations and experimental results.

Dual-Band Branch-Line Coupler With Port Extensions

A new branch-line coupler structure with port extensions is proposed for the dual-band operation. The conventional branch-line coupler structure is adapted to the dual-band operation by inserting a transmission line section at the input ports and modifying the branch parameters. The dual-band performance of the proposed coupler is verified theoretically through the rigorous microwave circuit analysis and the exact design equations are derived in concise form. The design, simulation, and measurement results validate the dual-band capability of the proposed coupler with the same quadrature phase relation between the two band frequencies.

GPU ACCELERATED UNCONDITIONALLY STABLE CRANK-NICOLSON FDTD METHOD FOR THE ANALYSIS OF THREE-DIMENSIONAL MICROWAVE CIRCUITS

The programmable graphics processing unit (GPU) is employed to accelerate the unconditionally stable Crank-Nicolson flnite-difierence time-domain (CN-FDTD) method for the analysis of microwave circuits. In order to e-ciently solve the linear system from the CN-FDTD method at each time step, both the sparse matrix vector product (SMVP) and the arithmetic operations on vectors in the bi-conjugate gradient stabilized (Bi-CGSTAB) algorithm are performed with multiple processors of the GPU. Therefore, the GPU based BI-CGSTAB algorithm can signiflcantly speed up the CN-FDTD simulation due to parallel computing capability of modern GPUs. Numerical results demonstrate that this method is very efiective and a speedup factor of 10 can be achieved.

Physics-Based Compact Model for AlGaN/GaN MODFETs With Close-Formed $I$–$V$ and $C$–$V$ Characteristics

A set of explicit analytical solutions to the charge concentration, current, and capacitance characteristics of AlGaN/GaN MODFETs in different working regions is developed. First, a unified charge control expression applicable to both subthreshold regions and strong inversion regions is determined, while the parasitic channel effect in AlGaN layer is also taken into account. The onset voltage for this parasitic channel is estimated for the first time. Based on the improved charge control model, the current (I ds), the transconductance (gm), and the output conductance (gd) are given explicitly and are applicable in a wide bias range. Moreover, the gate-to-source capacitance (C gs ) and gate-to-drain capacitance (C gd) have been obtained analytically under various applied biases, and, consequently, the cutoff frequency can be predicted. The present model shows good agreement with the experimental data and is useful for microwave circuit design and analysis.

A variational method of estimating the total measurement error of microwave-circuit analyzers

A variational method of estimating the total measurement error of microwave-circuit analyzers is considered. The method is based on the variation of the instrumental errors of the analyzer with respect to their confidence intervals, provided that the measurable and measured quantities are related by its mathematical model.

Analysis of planar microwave circuits with lumped‐elements by CN‐FDTD

AbstractA three‐dimensional implementation of the lumped‐element by Crank‐Nicolson finite‐difference time‐domain (CN‐FDTD) algorithm has been presented in this article. Several examples of planar microwave circuits with lumped resistor, capacitor, and/or inductor are simulated and compared with traditional finite‐difference time‐domain method and measurements. The accuracy of CN‐FDTD implementation for lumped elements in this article has been verified. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 113–116, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23969

Efficient analysis of planar microwave circuits with mixed‐order prism vector finite macroelements

AbstractThis paper introduces a new concept of a mixed‐order prism macroelement, suitable for an efficient analysis of three‐dimensional planar microwave circuits, using two‐dimensional meshes and preprocessors. The mixed‐order concept used here implies arbitrary orders of variation in different directions and differs essentially from the well‐known mixed‐order approximation that is an integral part of every Whitney element. It is the existence of a related systematic theory of higher‐order vector finite elements, previously documented, that facilitates the introduction of such a concept. The second‐ and third‐order elements, derived by this approach, are successfully applied in the analysis of planar microwave circuits, rendering the application of finite element method in such problems still a favorable option. Copyright © 2008 John Wiley & Sons, Ltd.

A new two-dimensional C–V model for prediction of maximum frequency of oscillation (fmax) of deep submicron AlGaN/GaN HEMT for microwave and millimeter wave applications

An analytical two-dimensional capacitance–voltage model for AlGaN/GaN high electron mobility transistor (HEMTs) is developed, which is valid from a linear to saturation region. The gate source and gate drain capacitances are calculated for 120nm gate length including the effects of fringing field capacitances. We obtain a cut-off frequency (fT) of 120GHz and maximum frequency of oscillations (fmax) of 160GHz. The model is very useful for microwave circuit design and analysis. Additionally, these devices allow a high operating voltage VDS, which is demonstrated in the present analysis. These results show an excellent agreement when compared with the experimental data.

A Calibration Approach for the Segmentation and Analysis of Microwave Circuits

This paper introduces a general method for the analysis of the individual blocks forming a complex circuit by measurements or simulations carried out on the whole. This is useful in those situations where the analysis of the single blocks is difficult. Paradoxically, the analysis of more complex structures, which contain individual elements, as subcircuits is, in some circumstances, easier to perform or may even be the only way to acquire information about the individual elements. Under certain conditions, the elements can be combined to obtain different circuits according to classic segmentation technique. Owing to its formulation, the method is applicable to both simulation and measurement problems.

A Quadrature-Sampled Pre-Corrected FFT for the Analysis of Microwave Circuits in Layered Media

This paper presents a fast iterative solution based on the quadrature sampled pre-corrected fast fourier transform (QSPCFFT) algorithm used to accelerate a method of moment discretization of the mixed potential integral equation (MPIE) for the analysis of circuits printed in a layered medium. The QSPCFFT algorithm is applied to accelerate the computation of all far interactions, and has a complexity that scales as O (N log N) and memory that scales as O(N). The algorithm is efficiently applied to broad-band analysis of printed circuits since the far-field is not constrained by the wavelength, but is determined rather by the local discretization.

Analysis of Nonlinear Microwave Circuits by Particle Swarm Algorithm

In this paper, the particle swarm algorithm is applied to the analysis of nonlinear microwave circuits. It should be emphasized that the particle swarm algorithm of this study is utilized for analyzing nonlinear microwave circuits, but not for optimization. The problem of analyzing a nonlinear microwave circuit was successfully transformed into the minimization of a scalar fitness function. This scalar fitness function is then minimized by particle swarm algorithm. Numerical simulation shows that the results calculated by this study are consistent with those calculated by the harmonic balance technique. Our analysis is very efficient and straightforward. In addition, our analysis imposes no limitation on the nonlinearity of microwave circuits. Therefore, this study can be applied to the analysis of many other nonlinear problems in electromagnetics.

Unconditionally stable Crank–Nicolson finite-different time-domain method for simulation of three-dimensional microwave circuits

An unconditionally stable Crank–Nicolson finite-difference time-domain (CN-FDTD) algorithm is presented for three-dimensional microwave circuit analysis. First, Mur's first–order absorbing boundary condition is applied this CN-FDTD algorithm. A symmetric successive over relaxation–preconditioned biconjugate-gradient algorithm is also proposed to solve the large sparse matrix equation obtained in the CN-FDTD method. Resonant cavity and several planar microstrip circuits are presented to illustrate the versatility of this technique. Numerical results indicate that with a time-step size excessively larger than the Courant–Friedrich–Levy limit, the accuracy of CN-FDTD is still much higher than that of the alternating-direction implicit FDTD.

EM-Based Monte Carlo Analysis and Yield Prediction of Microwave Circuits Using Linear-Input Neural-Output Space Mapping

A computationally efficient method for highly accurate electromagnetics-based statistical analysis and yield estimation of RF and microwave circuits is described in this paper. The statistical analysis is realized around a space-mapped nominal solution. Our method consists of applying a constrained Broyden-based linear input space-mapping approach to design, followed by an output neural space-mapping modeling process in which not only the responses, but the design parameters and independent variable are used as inputs to the output neural network. The output neural network is trained using reduced sets of training and testing data generated around the space-mapped nominal solution. We illustrate the accuracy and efficiency of our technique through the design and statistical analysis of a classical synthetic problem and a microstrip notch filter with mitered bends

An Empirical Bipolar Device Nonlinear Noise Modeling Approach for Large-Signal Microwave Circuit Analysis

An empirical bipolar transistor nonlinear noise model for the large-signal (LS) noise analysis of microwave circuits is described. The model is derived according to the charge-controlled nonlinear noise behavioral modeling approach, and includes nonlinearly controlled equivalent noise (EN) generators describing the low-frequency (LF) noise up-conversion encountered in LS RF operation. LS-modulated shot-noise sources and parametric LF noise in parasitic resistors are also taken into account for improved model accuracy. Details for the implementation of the proposed cyclostationary EN generators in the framework of a computer-aided design tool are presented. As an application example, a simplified version of the proposed nonlinear noise model for two GaInP-GaAs HBTs has been formulated and empirically characterized on the basis of both bias-dependent LF noise and phase-noise measurements. Measured and simulated noise performance of a monolithic voltage-controlled oscillator over a set of different operating conditions is shown for the validation of the proposed approach

Transient and Steady-State Analysis of Nonlinear RF and Microwave Circuits

This paper offers a review of simulation methods currently available for the transient and steady-state analysis of nonlinear RF and microwave circuits. The most general method continues to be the time-marching approach used in Spice, but more recent methods based on multiple time dimensions are particularly effective for RF and microwave circuits. We derive nodal formulations for the most widely used multiple time dimension methods. We put special emphasis on methods for the analysis of oscillators based in the warped multitime partial differential equations (WaMPDE) approach. Case studies of a Colpitts oscillator and a voltage controlled Clapp-Gouriet oscillator are presented and discussed. The accuracy of the amplitude and phase of these methods is investigated. It is shown that the exploitation of frequency-domain latency reduces the computational effort.

A stable algorithm for interfacing active and nonlinear devices with the ADI-FDTD method

This letter presents the algorithm to include active and nonlinear lumped devices in three-dimensional alternating-direction-implicit finite-difference time-domain simulations. The late-instability is considered and a late-stable algorithm is proposed. Numerical experiments validate the robustness of this algorithm. It can be applied to the analysis of radio frequency and microwave circuits.

Design study of piezoelectric micro-machined mechanically coupled cantilever filters using a combined finite element and microwave circuit analysis

A new mechanical filter structure is presented which comprises two silicon cantilevers mechanically coupled by a silicon linkage with thin film piezoelectric transducers providing electrical input and output signals. The resonance behaviour of such a structure results in a band-pass filter response, having a band-width determined by the frequency separation between the closely spaced in-phase and out-of-phase vibrational modes of the two coupled cantilevers. A detailed configuration design analysis, filter simulation and optimisation of performance is undertaken using a new modelling approach combining microwave circuit theory and finite element analysis to evaluate the generalised ( A, B, C and D) and scattering ( S) circuit parameters of the filter. Two significant features of the filters have emerged from the derived analyses and simulations: (1) with correct design filter Q-values can reach several thousand which is much higher than the Q-values (∼80) of uncoupled cantilevers, (2) the Q-value is determined by the configuration of the silicon linkage and so is under the designer's control. The position and length of the linkage that give optimum Q and minimum insertion loss are determined.

A parallel FFT accelerated transient field-circuit simulator

A novel fast electromagnetic field-circuit simulator that permits the full-wave modeling of transients in nonlinear microwave circuits is proposed. This time-domain simulator is composed of two components: 1) a full-wave solver that models interactions of electromagnetic fields with conducting surfaces and finite dielectric volumes by solving time-domain surface and volume electric field integral equations, respectively, and 2) a circuit solver that models field interactions with lumped circuits, which are potentially active and nonlinear, by solving Kirchoff's equations through modified nodal analysis. These field and circuit analysis components are consistently interfaced and the resulting coupled set of nonlinear equations is evolved in time by a multidimensional Newton-Raphson scheme. The solution procedure is accelerated by allocating field- and circuit-related computations across the processors of a distributed-memory cluster, which communicate using the message-passing interface standard. Furthermore, the electromagnetic field solver, whose demand for computational resources far outpaces that of the circuit solver, is accelerated by a fast Fourier transform (FFT)-based algorithm, viz. the time-domain adaptive integral method. The resulting parallel FFT accelerated transient field-circuit simulator is applied to the analysis of various active and nonlinear microwave circuits, including power-combining arrays.

A multiresolution method of moments for triangular meshes

This paper presents the construction, use, and properties of a multiresolution (wavelet) basis for the method of moments (MoM) analysis of metal antennas, scatterers, and microwave circuits discretized by triangular meshes. Several application examples show fast convergence of iterative solvers and accurate solutions with highly sparse MoM matrices. The proposed basis is organized in hierarchical levels, and keeps the different scales of the problem directly into the basis functions representation; the current is divided into a solenoidal and a quasi-irrotational part, which allows mapping these two vector parts onto fully scalar quantities, where the wavelets are defined. As a byproduct, this paper also presents a way to construct hierarchical sets of Rao-Wilton-Glisson (RWG) functions on a family of meshes obtained by subsequent refinement, i.e., with the RWG of coarser meshes expressed as linear combinations of those of finer meshes.