Application of asymptotic waveform evaluation for analysis of skineffect in lossy interconnects

Asymptotic waveform evaluation (AWE) is a technique for time-domain analysis of electrical interconnects. AWE is a computationally efficient method that asymptotically approximates the response of a large system with a lower-order transfer function. Asymptotic waveform evaluation is used to analyze lossy interconnects including the skin effect. The internal impedance of the interconnect conductors varies as a function of the square root of the frequency. First, an overview of AWE is presented. The AWE formulation for modeling frequency dependent loss in the conductors is derived using two different series expansions of the system response at both s=0 and s≠0 in the Laplace domain. The expansions for s≠0 are determined using a transfer function formulated for inclusion of the frequency-dependent internal impedance. The network response is computed by extracting the dominant poles and residues using the Pade approximation. The proposed method is evaluated using time-domain examples of lossy multiconductor transmission lines     

Fast RCS computation over a frequency band using method of momentsin conjunction with asymptotic waveform evaluation technique

The method of moments (MoM) in conjunction with the asymptotic waveform evaluation (AWE) technique is applied to obtain the radar cross section (RCS) of an arbitrarily shaped three-dimensional (3-D) perfect electric conductor (PEC) body over a frequency band. The electric field integral equation (EFIE) is solved using the MoM to obtain the equivalent surface current on the PEC body. In the AWE technique, the equivalent surface current is expanded in a Taylor's series around a frequency in the desired frequency band. The Taylor series coefficients are then matched via the Pade approximation to a rational function. Using the rational function, the surface current is obtained at any frequency within the frequency range, which is in turn used to calculate the RCS of the 3-D PEC body. A rational function approximation is also obtained using the model-based parameter estimation (MBPE) method and compared with the Pade approximation. Numerical results for a square plate, a cube, and a sphere are presented over a frequency bandwidth. Good agreement between the AWE and the exact solution over the bandwidth is observed     

渐近波形估计技术在线天线分析中的应用

叙述了矩量法(MOM)结合渐近波形估计(AWE)技术快速求解天线宽带输入阻抗的一般步骤,并将AWE技术拓展应用到阵列方向图的求解中.AWE技术的计算结果与经典矩量法计算的结果和SuperNEC的仿真结果比较,三者吻合很好,从而证明了该方法的精确性,同时也显现出了渐近波形估计技术可以大大减少计算时间的优势.     

Implementation of anisotropic PML for frequency domain FEM solution of discontinuity in dielectric waveguide

The anisotropic Perfectly Matched Layer(PML) absorbing boundary condition is implemented in a 2-D finite element formulation to solve dielectric waveguide discontinuity problems. The choice of parameters of anisotropic PML has been investigated. Using the boundary truncating technique, the solution process of Finite-Element Method (FEM) has been greatly simplified compared with other hybrid methods. The required computational resources have also significantly declined since the anisotropic PML interface can be placed much closer to the scatterer compared to other well known artificial boundary.     

Rapid solution of parameter-dependent linear systems for electromagnetic problems in the frequency domain

The minimal residual interpolation method reduces the number of iterations in an iterative method for multiple right-hand sides. It uses computed solutions to initialize an iterative solver with an accurate guess. This work demonstrates the efficiency of the method for frequency sweeps and solving scattering problems by plane waves incident from multiple angles. A bound on the number of solutions required for plane wave scattering before the remaining solutions obtained by minimal residual interpolation only is given. We discuss the performance of the method compared to iterative seed techniques. In a numerical example, a reduction factor of 60 is obtained on the number of matrix vector multiplications.     

A new discrete transmission line model for passive model orderreduction and macromodeling of high-speed interconnections

A new, computationally efficient, discrete model is presented for passive model order reduction of high-speed interconnections. The proposed discrete model is based on the use of the theory of compact finite differences for the development of the discrete approximation to the transmission line equations that govern wave propagation on the interconnections. Thus result in a discrete model that utilizes only a few unknowns per wavelength and yet provides highly accurate waveform resolution. In addition to improved computational efficiency, the generated discrete model is passive, and compatible with the passive reduced-order interconnect modeling algorithm (PRIMA). Thus, it is suitable for the development of passive reduced-order models of interconnection networks of high complexity. Numerical experiments from the simulation and model order reduction of coupled interconnections are used to illustrate the validity and efficiency of the proposed model     

Fast computation of wideband RCS using characteristic basis function method and asymptotic waveform evaluation technique

The Asymptotic Waveform Evaluation (AWE) technique is an extrapolation method that provides a reduced-order model of linear system and has already been successfully used to analyze wideband electromagnetic scattering problems. As the number of unknowns increases, the size of Method Of Moments (MOM) impedance matrix grows very rapidly, so it is a prohibitive task for the computation of wideband Radar Cross Section (RCS) from electrically large object or multi-objects using the traditional AWE technique that needs to solve directly matrix inversion. In this paper, an AWE technique based on the Characteristic Basis Function (CBF) method, which can reduce the matrix size to a manageable size for direct matrix inversion, is proposed to analyze electromagnetic scattering from multi-objects over a given frequency band. Numerical examples are presented to illustrate the computational accuracy and efficiency of the proposed method.     

基于频域广义传输矩阵方法的电磁散射特性分析

多尺度复杂电子系统的电磁场问题难以用单一的计算电磁学方法进行高效数值计算.基于区域分解方法和惠更斯等效原理,提出了频域广义传输矩阵（generalized transition matrix,GTM）方法:将系统分解为多个子模块,通过电场积分方程（electric field integreal equation,EFIE）把各个子模块的电磁特性进行提炼,再考虑所有子模块之间的电磁耦合,计算系统整体电磁场分布.GTM方法把多尺度问题转化为尺度相对比较单一的问题进行处理,在分析各种复合结构、非均匀各向异性介质、大型相控阵天线等电磁散射特性时,提供了灵活的解决方案.论文给出了GTM在手征介质、开口腔体以及Vivaldi相控阵天线电磁特性分析中的应用算例,当未知量个数压缩到原来的十分之一时,GTM计算结果与直接用矩量法（methed of moment,MoM）求解的计算结果非常吻合.GTM可以简洁地表示目标问题的电磁散射特征,与传统MoM相比,大幅度减少了基函数的数量,具有较高的计算精度和效率.     

基于有限元方法的波导管结构电磁屏蔽屏蔽效能分析

提出一种在屏蔽箱体孔缝结构的外部增加截止波导管结构的方法,利用截止波导管对高频电磁波的衰减作用来提高屏蔽箱体屏蔽效能。基于有限元法分别对截止波导管的长度、厚度及其形状进行仿真,仿真结果表明:在0.1 GHz~1 GHz频率范围内,随着截止波导管长度及厚度的增加屏蔽箱体屏蔽效能提高15d B以上,圆形和矩形截止波导管对屏蔽效能影响不大。根据实际情况合理选择截止波导管的长度及厚度可以提高微弱信号处理电路的电磁抗干扰能力。     

Experimental research of extraneous electromagnetic emissions by computing units in the frequency domain

Experimental research of extraneous electromagnetic emissions by computing units in the 15–1000 MHz frequency domain is conducted. It is shown that in order to correctly determine the range of radioelectronic intelligence it is reasonable to use weakly radiating cable line as the leaking wave antenna.     

三频段准连续波雷达信号目标检测性能分析

准连续波雷达是一种低截获概率雷达,结合了脉冲雷达收发隔离和连续波雷达截获概率低的优点,但其检测性能的优劣很大程度依赖于信号形式,普通的编码信号和线性调频信号已经不能满足其对目标探测的要求。为解决这个问题,设计了一种三频段信号和与之相应的收发系统,对系统结构及三频段信号的参数选择原则、目标检测原理、模糊函数、抗近距离盲区性能做了详细分析,并指出了三频段信号相对于相位编码信号和分时发射信号的优势所在,最后通过仿真证明,将三频段信号应用于准连续波体制雷达中时能准确探测目标,得到目标的各个参数并且能有效消除近距离盲区。     

Mixed time/frequency domain approach to model reduction

The letter considers the problem of reducing the transfer function of a given system to a lower order. The approach proposed appears to be suitable in cases where both the frequency-domain and the time-domain characteristics of the given system are to be preserved in the reduced order model.     

Time domain electromagnetic simulation for microwave CADapplications

Recent progress in time domain modeling is highlighted. Basic properties of time-domain simulators are reviewed, and techniques for improving computational efficiency are examined. The use of numerical synthesis through time reversal is discussed. The user interface is briefly considered and typical simulation results are given     

Application of asymptotic waveform evaluation to eigenmode expansion method for analysis of simultaneous switching noise in printed circuit boards (PCBs)

In this paper, the asymptotic waveform evaluation (AWE) technique is first applied to the conventional eigenmode expansion method for characterizing a power/ground (P/G) plane pair and analyzing the simultaneous switching noise on such plane pairs for printed circuit boards or multichip modules. The application of AWE avoids a large number of iterations in computing the impedance frequency response of a P/G plane pair structure and greatly reduces the computation time. Meanwhile, to obtain an accurate solution in an entire frequency range, we employ the complex frequency hopping technique which can help select multiple expansion points. In addition, the proposed approach can also be used to characterize the P/G plane pair structures with irregular shapes. Three examples demonstrate its high efficiency and good accuracy.     

Dynamic NBTI lifetime model for inverter-like waveform

In this paper, a simple yet accurate NBTI lifetime model has been formulated for a pMOSFET working in dynamic AC condition. The model is based on detailed dynamic NBTI (DNBTI) characterization for inverter-like waveform stress. The fitting parameters of the model can be readily obtained from the calibration of one-time DNBTI lifetime measurement for a small set of frequency/duty cycle matrix. After that, it can be employed to estimate the NBTI lifetime for a pMOSFET under any AC operating condition with reasonably good agreement. Additionally, it is shown that the lifetime enhancement by a shorter duty cycle is even more significant than that by a higher frequency. The application of the model to the lifetime estimation of circuits with multiple operation modes is also discussed.     

Recursive asymptotic impedance matrix method for electromagnetic waves in bianisotropic media

A recursive asymptotic impedance matrix method is presented for simple and stable analysis of electromagnetic waves in bianisotropic media. The method overcomes the numerical instability problem associated with the transition matrix method. It requires only elementary matrix operations along with thin-layer asymptotic approximation and bypasses the intricacies of the eigenvalue-eigenvector approach. Exploitation of its self-recursion algorithm with geometric subdivision of a layer leads to high computation efficiency. The method also facilitates the trade-off between accuracy and speed for various applications.     

为传感器测量提供灵活的频率调谐功能的数字波形发生器

可变电阻传感器可以将一个固定的直流激励电压或电流变换成一个被测量直接函数的电流或电压，在另一类传感器中移动物体或流体可以通过改变一个LC电路的电感值或电容值来产生一个传感器信号，图1示出了一个基本的交流驱动调谐电路接近式传感器1即L和C)以及采样电阻器R。     

针对非合作目标的调频步进编码波形设计方法

雷达对于非合作目标的探测,存在目标微小与速度未知两大困难,而相干积累的方法需要准确探测目标速度,并进行速度补偿,实际应用过程中效果受限。针对此问题提出了一种调频步进编码波形设计方法,可以在速度未知情况下脉间积累,同时在准确测量速度后宽带合成。首先研究线性调频子脉冲的距离速度耦合特性,通过波形设计抵消脉间目标运动成像位置变化;然后研究调频步进编码波形的宽带合成技术,使所得的高分辨一维距离像无距离混叠。最后,数值仿真实验验证了所提出波形的优势与应用价值。     

频带FSO-OFDM系统建模与LS信道估计研究

本文首先设计了频带FSO-OFDM系统模型,阐述了其发射和接收部分工作原理,介绍了大气散射信道模型。通过对散射信道的仿真,发现FSO-OFDM系统对弱散射有很强的抵御能力,当散射强度强时,系统性能就会急剧恶化,由于提高发射功率不能有效的降低散射对系统的影响,为了解决此问题,本文利用璩算法对导频处大气信道进行估计,最后通过插值恢复出数据处信道参数,通过仿真进行验证,结果表明,通过合理设计导频序列,IS算法能够很好的改善强散射信道中频带FSO-OFDM系统性能。     

An integral E-field accuracy test for high frequency asymptotic solutions

The increasing use of conformal slot arrays has generated considerable interest in the analysis of radiation on cylindrical structures. Since 1974, three different asymptotic solutions to the problem of radiation on an infinite circular cylinder have been published. These solutions, whose accuracy increases as some parameter (such as the wavenumber) increases, have the unfortunate property that it is difficult to estimate their accuracy when finite frequencies are used. Previous attempts to achieve an accuracy test for evaluating asymptotic solutions resulted in a test that was qualitative in nature and highly dependent on the source region accuracy of the proposed solution. Through the use of Green's identities, a new test based on satisfaction of theE-field boundary condition is formulated. The proposed test is quantitative in nature, is straightforward in application, and displays a mixed local/global nature. Under some circumstances the test lends itself to application as an iterative equation for point-by-point improvement of a proposed solution.