Theory of field-excited networks

The analysis of the transient response of multiconductor transmission line networks excited by electromagnetic (EM) fields can be performed either in the time- or in the frequency-domain. The transient analysis of field-excited networks having complex configurations and nonlinear loads is performed by using a combined frequency- and time-domain procedure. The simulation models of the line-sections are defined in the frequency-domain based on the exact formulation of Maxwell's equations. New expressions of the per-unit-length (p.u.l.) series impedances and shunt admittances are used in order to overcome the limitation of the Carson (1926) formulation in the case of a poorly conducting ground-plane and in the presence of very fast transients. An efficient procedure is applied for reducing the computation effort of the procedure in the case of complex large-dimension networks. Calculations are carried out to predict the overvoltages induced by an EMP-plane wave on a 20 kV-power network above a highly lossy ground and on a signal 18-port-multiconductor network     

Small signal equivalent circuit modeling of resonant converters

A general analytical procedure is presented for the equivalent circuit modeling of resonant converters, using the series and parallel resonant converters as examples. The switched tank elements of a resonant converter are modeled by a lumped parameter equivalent circuit. The tank element circuit model consists, in general, of discrete energy states, but may be approximated by a low-frequency continuous time model. These equivalent circuit models completely characterize the terminal behavior of the converters and are solvable for any transfer function or impedance of interest. With the approximate model it is possible to predict the lumped parameter poles and zeros, and to quickly determine the relevant DC gains of the output impedance and the control to output transfer function. Closed-form solutions are given for the equivalent circuit models of both converter examples. Experimental verification is presented for the control-to-output transfer functions of both series and parallel resonant converters, and good agreement between theoretical prediction and experimental measurement is obtained     

Interconnection of Subsystem Reduced-Order Models in the Electrothermal Analysis of Large Systems

Heat conduction in an electronic device is commonly modeled as a discretized thermal system (e.g., finite element or finite difference models) that typically uses large matrices for solving complex problems. The large size of electronic-system heat transfer models can be reduced using model reduction methods and the resulting reduced-order models can yield accurate results with far less computational costs. Electronic devices are typically composed of components, like chips, printed circuit boards, and heat sinks that are coupled together. There are two ways of creating reduced-order models for devices that have many coupled components. The first way is to create a single reduced-order model of the entire device. The second way is to interconnect reduced-order models of the components that constitute the device. The second choice (which we call the "reduce then interconnect" approach) allows the heat transfer specialist to perform quick simulations of different architectures of the device by using a library of reduced-order models of the different components that make up the device. However, interconnecting reduced-order models in a straightforward manner can result in unstable behavior. The purpose of this paper is two-fold: creating reduced-order models of the components using a Krylov subspace algorithm and interconnecting the reduced-order models in a stable manner using concepts from control theory. In this paper, we explain the logic behind the "reduce then interconnect" approach, formulate a control-theoretic method for it, and finally exhibit the whole process numerically, by applying it to an example heat conduction problem     

Empirical frequency-domain optimal parameter estimate for black-box processes

Most of the previous signal processing identification results have been achieved using either time-domain or frequency-domain algorithms. In this study, the two methods were combined to create a novel identification algorithm called the empirical frequency-domain optimal parameter (EFOP) estimate and the recursive EFOP algorithm for common linear stochastic systems disturbed with noise. A general prediction error criterion was introduced in the time-domain estimate. By minimizing the frequency-domain estimate, some general prediction error criteria were constructed for Black-box models. Then, the parameter estimation was obtained by minimizing the general prediction error criterion. This method theoretically provides the globally optimum frequency-domain estimate of the model. It has advantages in anti-disturbance performance, and can precisely identify a model with fewer sample numbers. Lastly, some simulations were carried out to demonstrate the validity of the new method.     

Efficient time-domain beam-propagation method for modelingintegrated optical devices

A new efficient technique that models the behavior of pulsed optical beams in homogenous medium, metallic and dielectric waveguides, is introduced and verified using both linear nondispersive and dispersive examples that have analytical predictions. Excellent accuracy results have been observed. The method is called time-domain beam-propagation method (TD-BPM) because it is similar to the classical continuous-wave BPM with additional time dependence. The explicit finite difference and the Du Fort-Frankel approaches were used to discretize the TD-BPM equation. Comparisons between these techniques are also given with the application of the perfectly matched layers as spatial boundary conditions to the Du Fort-Frankel. Then the TD-BPM was successfully applied to model a two-dimensional dielectric Y-junction. It is concluded that the new technique is more efficient than the traditional finite-difference TD method, especially in modeling large optical devices     

Inherent Signal Losses in R.esistive-Diode Mixers

A new time-domain method is presented for the characterization and analysis of resistive-diode mixers. The method has been found to be helpful in evaluating experimental models of new mixer designs. From an analytical viewpoint, this method has provided some new insights into mixer behavior and the fundamental limits to mixer performance. In analyzing equivalent mixer models, the method has been found to be in agreement with the classical frequency-domain approach. In using the time-domain method to determine the minimum available loss, theoretical studies were made using an "ideal-diode" model which is presumed to have zero forward-bias resistance and infinite reverse-bias impedance. Significant signal losses were found to occur, even in this "lossless" condition, when reactive filtering was used to suppress unwanted frequency responses. The lost signal power was not reflected and it did not appear at other signal-related frequencies. This result has also been found in a frequency-domain analysis using a new formulation suggested to the author in private correspondence. This loss is explained in two different ways, depending upon the model used and the method of analysis. In one example, using the time-domain approach, it was found that signal energy is converted into dc in the rectified current. In the frequency domain analysis, the loss is explained as the result of frequency conversions into a large number of high-order modulation products. The paper includes some newly formulated conjectures concerning the ultimate limits on conversion loss in single-diode mixers.     

Charge-domain integrated circuits for signal processing

A new class of integrated circuits called charge-domain device has been developed for performing enhanced monolithic signal processing. All signal-processing operations are accomplished by splitting, routing and combining charge packets, thus overcoming many of the limitations of alternative devices such as charge-coupled device (CCD) split-electrode transversal filters and switched capacitor filters. Charge manipulation techniques are described which allow poles as well as zeros of a transfer function to be implemented efficiently, leading to infinite impulse response monolithic filters suitable for high-frequency applications. Several test filters, including a narrowband 8-pole bandpass filter, are demonstrated. These charge-domain devices are useful in applications ranging from radio IF to radar to video signal processing with a high level of integration achievable on a single charge-domain integrated circuit.     

Time-domain antenna characterizations

A set of time-domain characterizations that can efficiently describe wireband antennas is proposed. The experimentally measured responses of transverse electromagnetic horn antennas are used to evaluate the utility of these characterizations. Comparisons are made between the antennas' frequency-domain response and their time-domain characterizations. The comparisons show that the time-domain characterizations can provide significant insight into an antenna's behavior as well as providing a means to accurately compare two or more different antennas     

The sliding DFT

The sliding DFT process for spectrum analysis was presented and shown to be more efficient than the popular Goertzel (1958) algorithm for sample-by-sample DFT bin computations. The sliding DFT provides computational advantages over the traditional DFT or FFT for many applications requiring successive output calculations, especially when only a subset of the DFT output bins are required. Methods for output stabilization as well as time-domain data windowing by means of frequency-domain convolution were also discussed. A modified sliding DFT algorithm, called the sliding Goertzel DFT, was proposed to further reduce the computational workload. We start our sliding DFT discussion by providing a review of the Goertzel algorithm and use its behavior as a yardstick to evaluate the performance of the sliding DFT technique. We examine stability issues regarding the sliding DFT implementation as well as review the process of frequency-domain convolution to accomplish time-domain windowing. Finally, a modified sliding DFT structure is proposed that provides improved computational efficiency.     

Performance of MODFET and MESFET, a comparative study includingequivalent circuits using combined electromagnetic and solid-statesimulator

A combined electromagnetic and solid-state (CESS) simulation model for the analysis of submicrometer semiconductor devices including the electromagnetic-wave propagation effects is presented. The performance comparison of two important high-frequency devices-modulation doped field-effect transistor (MODFET) and metal-semiconductor field-effect transistor (MESFET)-are illustrated using this model. The CESS simulator couples a semiconductor model to the three-dimensional (3-D) time-domain solution of Maxwell's equations. The semiconductor model is based on the moments of the Boltzmann's transport equation. The simulation uses the electromagnetic-wave concept to emphasize the better performance of MODFET over MESFET. The electromagnetic-wave propagation effects on the two devices are thoroughly analyzed. The use of the electromagnetic model over the conventional quasi-static model provides the actual device response along the gatewidth at high frequencies. The exchange of energy between the electrons and the electromagnetic wave is observed. The CESS model also facilitates the optimum choice of the device width in terms of the output voltage. This model is capable of predicting the large-signal behaviour of the submicrometer devices as well. The equivalent-circuit parameters are extracted at high frequencies for MODFET and MESFET, using a time-domain approach as well as a quasi-static approach     

Improving time-domain measurements with a network analyzer using arobust rational interpolation technique

A method to efficiently and accurately compute a time-domain waveform from a network-analyzer frequency-domain measurement is presented in this paper. The method is based on a robust interpolation technique to construct a pole-residue representation of the response of the device-under-test. First, the rational function is expressed in terms of Chebyshev polynomials, instead of the usual power series, to accurately determine the poles of the network over a wide frequency range. The properties of a passive system are then utilized to efficiently calculate the residues. The resulting pole-residue model is analytically transformed to obtain the time-domain response in any time window, beyond the limitations of the discrete Fourier transform (DFT) technique. Unlike the DFT technique, the method does not require a large number of equally spaced harmonically related frequency points. The parametric model can also be used to economically store large measurement data. The proposed procedure is computationally inexpensive and less sensitive to numerical instability. To illustrate the validity of the method, examples of frequency- and time-domain measurements of a Beatty structure and simulation data of a low-pass Butterworth filter are given     

Tunable/adaptive second-order IIR notch filter

A modified second-order infinite impulse response (IIR) notch filter with constrained poles and zeros is presented to eliminate or retrieve sinusoids embedded in a broadband signal. Such a filter is ideally suited to either parallel or cascaded implementation. Two classes of problems are considered. The first is where the sinusoidal frequencies are known a priori. For this case a straightforward design procedure based on a set of design characteristic graphs is used to select tunable notch filter parameters. An interesting property of the notch filter model is that it can be converted to a line enhancer by interchanging the position of the poles and zeros. The second type of problem arises when the sinusoidal frequencies are unknown and possibly varying with time. This means that an adaptive solution is required and an important consideration is the parameter estimation accuracy. For this purpose, the paper derives the Cramer–Rao lower bound for the adaptive cascaded notch filter using a frequency-domain approach. Some simulation results are included to demonstrate the effectiveness of the proposed adaptive notch filter.     

设备级线缆强电磁辐照敏感度仿真分析

针对近年来复杂电磁环境中强电磁脉冲攻击,研究得出设备级强电磁辐照敏感度仿真分析方法。该方法采用3D电磁场仿真及2D电路仿真相结合的手段,通过建立几何模型、定义材料参数、添加负载及激励源、放置监测探头等步骤,最终仿真得出设备外壳内部及线缆上耦合电流的时域、频域特性。由仿真结果可知,设备内部及线缆上耦合的电压、电流在极短时间内即可达到具有破坏性的峰值,且其同时具备较宽的频谱,从而可对多种电子设备造成毁伤。因此,当电子设备处在复杂电磁环境强电磁脉冲攻击下,必须采取一定的强电磁保护措施。本仿真方法也可适用其他通用电子设备强电磁辐照敏感度仿真分析。     

Transient analysis of electromagnetic systems with multiple lumped nonlinear loads

A novel method for transient analysis of electromagnetic systems with multiple lumped nonlinear loads is presented. The uniqueness of this approach is that we develop time-domain Green's functions for the multiport linear part of the electromagnetic system by suitably terminating the ports. This ensures a short duration of Green's functions. Hence the amount of frequency-domain data necessary to obtain the time-domain Green's functions is modest. The application of this technique to an arbitrary excitation is just a straightforward convolution. With this technique one can analyze responses of systems with arbitrary nonlinear loads (even with memory) as we have at any time instant Thevenin's equivalent of the linear portion of the electromagnetic system. Examples are presented to illustrate the application of this technique to multiport nonlinearly loaded antennas.     

A new procedure for interfacing the transmission line matrix (TLM)method with frequency-domain solutions

The authors present a new procedure that interfaces the transmission-line matrix (TLM) method with frequency-domain solutions of electromagnetic fields. Frequency-domain solutions are transformed into appropriate time-domain sequences using the discrete Fourier transform (DFT). Hence, the corresponding boundary Johns matrix can be determined with minimum computational effort. The subsequent treatment consists in convolving the streams of TLM impulses incident on the boundary with a Johns matrix generated with the new approach. The method is used to obtain the time-domain reflection sequence of wideband absorbing terminations in a rectangular waveguide in the dominant mode operation. In addition, the time-domain analysis of pulse penetration through a sheet with high, but finite, conductivity is presented. Good results demonstrate the efficiency of the proposed procedure     

The expansion wave concept. I. Efficient calculation of spatialGreen's functions in a stratified dielectric medium

A procedure is given to perform the inverse Fourier transformation relating a spatial Green's function to its spectral equivalent. The procedure is applied to the spectral Green's functions of the double scalar mixed-potential integral expression formulation of the electromagnetic field in a stratified dielectric medium. The extraction technique is used to annihilate every type of “problematic” behavior of the spectral Green's functions. Every annihilating function is inverse Fourier transformed analytically. It is shown that the annihilation of both the surface wave poles and the singularities at the branch point results in a set of analytical spatial functions, which are a very good approximation of the exact spatial Green's function down to relatively small lateral distances     

Pruning the Volterra Series for Behavioral Modeling of Power Amplifiers Using Physical Knowledge

This paper presents an efficient and effective approach to pruning the Volterra series for behavioral modeling of RF and microwave power amplifiers. Rather than adopting a pure "black-box" approach, this model pruning technique is derived from a physically meaningful block model, which has a clear linkage to the underlying physical behavior of the device. This allows all essential physical properties of the PA to be retained, but significantly reduces model complexity by removing unnecessary coefficients from the general Volterra series. A reduced-order model of this kind can be easily extracted from standard time/frequency-domain measurements or simulations, and may be simply implemented in system-level simulators. A complete physical analysis and a systematic derivation are presented, together with both computer simulations and experimental validations     

单端口天线散射理论研究

本文给出单端口天线的频域和时域散射理论分析,通过时域和频域分析清晰地说明了天线散射的机理.分析过程中包含了探测天线和接收天线对被测天线散射的影响.天线的时域散射特性直观地区分了结构模式项散射场和天线模式项散射场.以该分析过程和结论为基础,讨论了天线散射控制的指导思想.     

一种接收机非线性行为建模方法

提出一种基于多项式的接收机行为建模方法。采用Hammerstein模型构建接收机行为模型,分别用非线性模块与记忆线性模块表征接收机非线性特性和记忆效应;利用傅里叶级数和最小二乘法分别辨识行为模型的非线性模块参数与线性模块参数;最后通过接收机ADS模型仿真数据,验证所提出的接收机非线性行为建模方法。对比分析了ADS仿真和行为模型的AM-AM特性及单音时域波形,实验结果表明,接收机行为模型的AM-AM特征曲线及时域波形与ADS仿真数据吻合程度较好。本文方法可预测接收机的非线性响应,对在复杂电磁环境下的接收机非线性效应评估具有理论价值。