A fast hybrid field-circuit simulator for transient analysis of microwave circuits

A plane-wave-time-domain accelerated time-domain integral-equation solver is coupled to a SPICE-like transient circuit simulator to analyze electromagnetic platform-circuit interactions. The hybrid field-circuit simulator simultaneously solves surface-wire-volume time-domain integral equations that model electromagnetic interactions with the platform and modified nodal analysis equations that govern the behavior of the potentially nonlinear lumped circuits. A shielded nonlinear microwave amplifier is analyzed using the proposed scheme, and its immunity to electromagnetic interference is assessed.     

Fast and Rigorous Analysis of EMC/EMI Phenomena on Electrically Large and Complex Cable-Loaded Structures

A fast and comprehensive time-domain method for analyzing electromagnetic compatibility (EMC) and electromagnetic interference (EMI) phenomena on complex structures that involve electrically large platforms (e.g., vehicle shells) along with cable-interconnected antennas, shielding enclosures, and printed circuit boards is proposed. To efficiently simulate field interactions with such structures, three different solvers are hybridized: (1) a time-domain integral-equation (TDIE)-based field solver that computes fields on the exterior structure comprising platforms, antennas, enclosures, boards, and cable shields (external fields); (2) a modified nodal-analysis (MNA)-based circuit solver that computes currents and voltages on lumped circuits approximating cable connectors/loads; and (3) a TDIE-based transmission line solver that computes transmission line voltages and currents at cable terminations (guided fields). These three solvers are rigorously interfaced at the cable connectors/loads and along the cable shields; the resulting coupled system of equations is solved simultaneously at each time step. Computation of the external and guided fields, which constitutes the computational bottleneck of this approach, is accelerated using fast Fourier transform-based algorithms. Further acceleration is achieved by parallelizing the computation of external fields. The resulting hybrid solver permits the analysis of electrically large and geometrically intricate structures loaded with coaxial cables. The accuracy, efficiency, and versatility of the proposed solver are demonstrated by analyzing several EMC/EMI problems including interference between a log-periodic monopole array trailing an aircraft's wing and a monopole antenna mounted on its fuselage, coupling into coaxial cables connecting shielded printed circuit boards located inside a cockpit, and coupling into coaxial cables from a cell phone antenna located inside a fuselage.     

FD-TD modeling of digital signal propagation in 3-D circuits withpassive and active loads

Most existing computer-aided circuit design tools are limited when digital clock speeds exceed several hundred MHz. These tools may not deal effectively with the physics of UHF and microwave electromagnetic wave energy transport along metal surfaces such as ground planes or in the air away from metal paths that are common at or above this frequency range. In this paper, we discuss full-wave modeling of electronic circuits in three dimensions using the finite-difference time-domain (FD-TD) solution of Maxwell's equations. Parameters such as stripline complex line impedance, propagation constant, capacitance per unit length and inductance per unit length can be easily computed as a function of frequency. We also discuss FD-TD Maxwell's equations computational modeling of lumped-circuit loads and sources in 3-D, including resistors and resistive voltage sources, capacitors, inductors, diodes, and transistors. We believe that this approach will be useful in simulating the large-signal behavior of very high-speed nonlinear analog and digital devices in the context of the full-wave time-dependent electromagnetic field     

Analysis of power delivery network constructed by irregular-shaped power/ground plane including densely populated via-hole

The high speed and low power trend has imposed more and more importance on the design of the power distribution network (PDN) using multilayer printed circuit boards (PCBs) for modern microelectronic packages. This paper presents a fast and efficient analysis methodology in frequency domain for the design of a PDN with a power/ground plane pair, which considers the effect of irregular shape of the power/ground plane and densely populated via-holes. The presented method uses parallel-plate transmission line theory with equivalent circuit model of unit-cell grid considering three-dimensional geometric boundary conditions. Characteristics of PDNs implemented by perforated planes including a densely populated via-hole structure is quantitatively determined based on full-wave analysis using the finite-difference time-domain (FDTD) periodic structure modeling method and full-wave electromagnetic field solver. Using a circuit simulator such as popularly used SPICE and equivalent circuit models for via-hole structure and perforations, the authors have analyzed input-impedance of the power/ground plane pair. Since the presented method gives an accurate and fast solution, it is very useful for an early design of multilayer PCBs.     

Analysis of Low-Frequency Electromagnetic Transients by an Extended Time-Domain Adaptive Integral Method

A stable and fast marching-on-in-time based integral-equation solver for analyzing low-frequency electromagnetic transients is presented. Stability and computational efficiency are achieved by using a frequency-normalized and diagonally balanced loop-tree decomposition scheme in concert with a novel fast Fourier transform (FFT)-based acceleration scheme. The proposed algorithm extends the time-domain adaptive integral method (TD-AIM) into the low-frequency regime by accelerating the computations of not only (discrete) "delayed" interactions due to fields observed one or more time steps after being generated but also "instantaneous" interactions due to fields observed less than one time step after being launched. This is realized by augmenting the four-dimensional blocked space-time FFTs in the TD-AIM recipe with three-dimensional space-only FFTs. Application of the extended TD-AIM accelerated integral-equation solver to the analysis of package geometries demonstrates its accuracy, stability, and efficiency.     

Incorporation of Multiport Lumped Networks Into the Hybrid Time-Domain Finite-Element Analysis

A systematic and efficient algorithm is presented for incorporating multiport lumped networks in terms of admittance matrices into a hybrid field-circuit solver based on the extended time-domain finite-element method. The Laplace-domain admittance matrices are cast into the time-domain stepping equations for port voltages and currents to form a lumped-network subsystem, which is then interfaced with the finite-element and circuit subsystems through shared ports. While the port voltages of the lumped-network subsystem are determined by the finite-element and circuit subsystems, its port currents are treated as external current excitations for the finite-element and circuit subsystems. All the lumped-network port variables are then eliminated from the final expressions to form a global system for only the finite-element and circuit unknowns. The proposed algorithm further extends the capability of the existing field-circuit solver to model more complex and mixed-scale hybrid circuits, and the algorithm is validated and demonstrated through numerical examples.      

Circuit-based versus full-wave modelling of active microwave circuits

Modern full-wave computational tools enable rigorous simulations of linear parts of complex microwave circuits within minutes, taking into account all physical electromagnetic (EM) phenomena. Non-linear components and other discrete elements of the hybrid microwave circuit are then easily added within the circuit simulator. This combined full-wave and circuit-based analysis is a must in the final stages of the circuit design, although initial designs and optimisations are still faster and more comfortably done completely in the circuit-based environment, which offers real-time solutions at the expense of accuracy. However, due to insufficient information and general lack of specific case studies, practitioners still struggle when choosing an appropriate analysis method, or a component model, because different choices lead to different solutions, often with uncertain accuracy and unexplained discrepancies arising between the simulations and measurements. We here design a reconfigurable power amplifier, as a case study, using both circuit-based solver and a full-wave EM solver. We compare numerical simulations with measurements on the manufactured prototypes, discussing the obtained differences, pointing out the importance of measured parameters de-embedding, appropriate modelling of discrete components and giving specific recipes for good modelling practices.     

金属接触非线性引起的无源互调效应的数值分析

针对时域物理光学方法求解无源互调问题的局限性,提出基于"场路结合"的数值分析方法,建立非线性金属结的等效电路模型并将其引入到全波方法中,通过全波方法与等效电路相结合的方式来分析系统的无源互调干扰.计算实例表明,该方法可以精确地计算由于金属接触非线性引起的无源互调及其作为二次辐射源所激发的电磁场,避免了时域方法在电大尺寸问题上计算的积累误差以及只能对处于远场区的简单微波结构的无源互调效应进行求解的问题.本文提出的场路结合数值分析方法为微波部件无源互调效应的研究提供了新的思路与方法.     

Full-wave simulation of electromagnetic coupling effects in RF and mixed-signal ICs using a time-domain finite-element method

This paper describes the computer simulation and modeling of distributed electromagnetic coupling effects in analog and mixed-signal integrated circuits. Distributed electromagnetic coupling effects include magnetic coupling of adjacent interconnects and/or planar spiral inductors, substrate coupling due to stray electric currents in a conductive substrate, and full-wave electromagnetic radiation. These coupling mechanisms are inclusively simulated by solving the full-wave Maxwell's equations using a three-dimensional (3-D) time-domain finite-element method. This simulation approach is quite general and can be used for circuit layouts that include isolation wells, guard rings, and 3-D metallic structures. A state-variable behavioral modeling procedure is used to construct simple linear models that mimic the distributed electromagnetic effects. These state-variable models can easily be incorporated into a VHDL-AMS simulation providing a means to include distributed electromagnetic effects into a circuit simulation.     

Circuit simulations combined with the electromagnetic fieldanalysis

In order to provide a means of rigorous simulation for wideband nonlinear microwave integrated circuits, the concept of a lumped device model is introduced into a three-dimensional, time-domain electromagnetic field analysis method. This makes it possible to perform both a circuit simulation including nonlinear lumped devices and an electromagnetic field analysis for distributed microwave components at the same time. As an example, the generation of picosecond pulses from a nonlinear transmission line circuit is simulated. Based on the results, the features and the validity of the method are discussed in comparison with conventional circuit simulations     

A new global time-domain electromagnetic simulator of microwavecircuits including lumped elements based on finite-element method

This paper proposes an extension of the finite-element time-domain method for the global electromagnetic analysis of complex inhomogeneous microwave distributed circuits, containing linear or nonlinear lumped elements. This technique combines Maxwell's equations and circuit equations, directly using SPICE software for the lumped part. Its validation is performed through the study of a strongly coupled two-element active antenna     

均匀介质中基于积分方程的二维电磁成像模拟

开发了一种基于积分方程的模拟均匀介质中二维电磁成像的反演算法。在反演中采用了Born 迭代方法,该算法具有抗噪声能力强、迭代稳定的优点。在正演计算中采用了计算积分方程的稳定型双共轭梯度快速Fourier 变换(BCGS-FFT)算法,将插值函数作为基函数和试探函数对积分方程进行弱化离散,离散后的积分方程采用稳定型双共轭梯度迭代方法进行求解,从而得到异常体内电场的分布,迭代过程中采用快速傅里叶变换(FFT)技术进行加速。反演算例说明了所开发算法的精确性和有效性。     

Circuit analysis of electromagnetic radiation and field couplingeffects for networks with embedded full-wave modules

With continually increasing operating frequencies, the analysis of electromagnetic interference (EMI)-related effects is becoming an important issue for high-speed designs. An algorithm is presented for fast analysis of radiation and incident field coupling effects in high-speed circuits. The proposed technique provides an efficient means for combining the solutions from full-wave field solvers such as the finite-difference time-domain (FDTD) method with circuit level simulators such as SPICE for calculating radiated/coupled fields in arbitrarily shaped interconnect structures. The technique speeds up the whole simulation process by employing a model-reduction-based approach, and also overcomes the numerical stability problems associated with the FDTD, in the presence of nonlinear terminations. In addition, the proposed algorithm provides a direct access to existing vast device libraries of SPICE in EMI analysis     

A two-dimensional transmission line matrix microwave fieldsimulator using new concepts and procedures

A two-dimensional field simulator for microwave circuit modeling is described. It incorporates a number of recently developed concepts and advanced transmission line matrix (TLM) procedures. In particular, a discrete Green's function concept based on P.B. John's and K. Akhlarzad's time-domain diakoptics is realized, providing a high level of processing power through modularization of large structures at the field level, simulation of wideband matched loads or absorbing walls, modeling of frequency-dispersive boundaries in the time domain, and large-scale numerical preprocessing of passive structures. Nonlinear field modeling concepts are also implemented in the TLM field simulator. It can analyze two-dimensional circuits of arbitrary geometry containing both linear and nonlinear media. The circuit topology is input graphically. Both time-domain and frequency-domain responses can be computed and displayed. The capabilities and limitations of the simulator are discussed, and several microstrip and waveguide components are modeled to demonstrate its important features     

求解场-路混合问题的时域积分方程法

研究了基于时域积分方程求解场-路混合问题的方法,其基础是“耦合电流”的思想,区域中的电路部分和电磁结构部分通过其连接处的耦合电流联系在一起,由此完善了传统的电流连续性方程.然后将TDIE方法与电路仿真方法——改进的节点分析法相结合,并通过广义基尔霍夫电压定律将电路中节点的电位与电磁结构上接口处的电位联系在一起.采用这种方法求解场-路混合问题,不需要生成端口模型,而直接求解场-路耦合方程.最后通过传输线算例证明了方法的正确性.     

A hierarchical FFT algorithm (HIL-FFT) for the fast analysis of transient electromagnetic scattering phenomena

A fast algorithm for accelerating the time-marching solution of time-domain integral equations pertinent to the analysis of free-space electromagnetic scattering from perfectly conducting, platelike and uniformly meshed structures is presented. The matrix-vector multiplications required by the time-marching scheme are accelerated by use of the fast Fourier transform (FFT). This acceleration is achieved in a multilevel fashion by hierarchically grouping sparse interactions to extract denser pieces that are efficiently evaluated by the FFT. The total computational cost and storage requirements of this algorithm scale as O(N/sub t/N/sub s/log/sup 2/ N/sub s/) and O(N/sup 1.5/), respectively, as opposed to O(N/sub t/N/sub s//sup 2/) and O(N/sub s//sup 2/) for classical time-marching methods (N/sub s/ and N/sub t/ denote the total number of spatial unknowns and time steps, respectively). Simulation results demonstrate the accuracy and efficiency of the algorithm.     

A coupled efficient and systematic full-wave time-domain macromodeling and circuit Simulation method for signal integrity analysis of high-speed interconnects

This paper presents an accurate and systematic approach for analysis of the signal integrity of the high-speed interconnects, which couples the full-wave finite difference time domain (FDTD) method with scattering (S) parameter based macromodeling by using rational function approximation and the circuit simulator. Firstly, the full-wave FDTD method is applied to characterize the interconnect subsystems, which is dedicated to extract the S parameters of the subnetwork consisting of interconnects with fairly complex geometry. Once the frequency-domain discrete data of the S parameters of the interconnect subnetwork is constructed, the rational function approximation is carried out to establish the macromodel of the interconnect subnetwork by employing the vector fitting method, which provides a more robust and accurate solution for the overall problem. Finally, the analysis of the signal integrity of the hybrid circuit can be fulfilled by using the S parameters based macromodel synthesis and simulation program with integrated circuits emphasis (SPICE) circuit simulator. Numerical experiments demonstrate that the proposed approach is accurate and efficient to address the hybrid electromagnetic (interconnect part) and circuit problems, in which the electromagnetic field effects are fully considered and the strength of SPICE circuit simulator is also exploited.     

Simulation and Design of Microwave Class-C Amplifiers through Harmonic Analysis

A method for analyzing microwave class-C amplifiers is proposed which satisfies the requirements of a wide application field, and, at the same time, operates with a fast runing time and without convergence problems. It is based on the partitioning of the circuit into linear and nonlinear subnetworks for which, respectively, frequency-domain and time-domain equations are written. Then, taking into account that the time-domain and frequency-domain representations are related by the Fourier series, the circuit behavior is described by means of a system of nonlinear equations whose unknowns are the harmonic components of the incident waves at all the connections. To overcome the numerical problems arising in the search for the solution of this system when strong nonlinearities are involved, a special step-by-step procedure is adopted. The problem is transformed into the search for the solution of a sequence of well-conditioned systems of equations corresponding to a sequence of well-chosen circuits obtained from the original one through progressive changes of the input signal starting from 0 up to the nominal value. The program which implements the method is also described and the results of the analysis relative to a class-C amplifier are compared with measured values.     

A systematic coupled approach for electromagnetic susceptibility analysis of a shielded device with multilayer circuitry

This paper presents a systematic coupled approach for electromagnetic susceptibility (EMS) analysis of a shielded electronic device in the presence of an ambient electromagnetic interference (EMI). A full-wave electromagnetic modeling technique coupled with a circuit-based method is developed for the overall EMS performance analysis. The mixed-potential electric field integral equation (MPIE) is formulated via the method of moments to model the electromagnetic properties of an arbitrary structure consisting of wires and surfaces with any applied excitation. With numerical analysis, the effect of an ambient electromagnetic noise is characterized, and an equivalent circuit model is extracted for further analysis of EMI to internal high-speed sensitive circuits. Numerous examinations exhibit that this systematic coupled approach is a computationally efficient method to address the EMS problems at system level, in which the external EMI effects are fully considered and the circuit-based simulator is also exploited.