An efficient characterization of interconnectedmulticonductor-transmisslon-line networks

The numerical solution of the multiconductor-transmission-line (MTL) equations for lossy interconnected transmission lines (TLs) is investigated in this paper. The solution for the transmission line segments is accomplished through the finite-difference time-domain method, whereas the terminations and interconnection networks (which may contain nonlinearities) are characterized with an efficient state-variable representation. High-frequency skin-effect losses in the TLs are included in the MTL equations through convolution integrals in the MTL equations. The computation of these convolution integrals represents the bulk of the solution effort. Two methods, the singular-value-decomposition method and the matrix-pencil method, are shown to significantly reduce the computation time and improve the solution accuracy     

Decoupling the multiconductor transmission line equations

A comprehensive discussion is presented of the method of decoupling the multiconductor transmission line (MTL) equations by the method of transformation of the voltages and currents to mode voltages and currents in order to obtain their general solution. Various ways of defining and obtaining the transformations are shown which serve to connect the myriad of such definitions and also point out where inconsistencies in those definitions can result. Structures for which the decoupling is assured are also discussed. The MTL equations to be decoupled are in the frequency domain, and extensions to their applicability in the time-domain are shown     

端接非线性负载的不等长传输线瞬态分析

对时域有限差分(FDTD)法应用于不等长多导体传输线端接非线性负载的情况进行了介绍.首先给出了多导体传输线电报方程和差分公式;然后介绍了不等长传输线的仿真模型;在此基础上,最后通过建立端接非线性负载的不等长多导体传输线模型,对该情况下传输线两端的电压响应进行了分析.数值仿真结果说明了FDTD法解决此类问题的正确性和有效性,为不等长传输线瞬态分析的进一步研究打下了基础.     

An inverted-microstrip resonator for human head proton MR imaging at 7 tesla

As an extension of the previously developed microstrip transmission line (MTL) RF coil design, a high-frequency RF volume coil using multiple inverted MTL (iMTL) resonators for human head imaging at high magnetic field strength of 7 tesla (T) is reported. Compared to conventional MTL resonators, iMTL resonators can operate at higher frequency with lower losses and, thus, are suitable for designs of high-frequency RF volume coils with large coil size for human MR imaging and spectroscopy at high fields. An approach using capacitive terminations was analyzed and applied to the design of the iMTL volume coil for improving RF field homogeneity and broadening frequency-tuning range. A performance-comparison study was conducted between the prototype iMTL volume coil and a custom-built TEM volume coil at 7 T. The iMTL volume coil presents a comparable SNR and intrinsic B1 homogeneity to the TEM volume coil. Phantom and the human head images acquired using the iMTL volume coil are also presented. The proposed iMTL volume coil provides an efficient and alternative solution to design high-frequency and large-size volume coils for human MR applications at very high fields.     

Modal transmission-line calculation of shielding effectiveness ofcomposite structures

A novel modal transmission-line (MTL) method for the calculation of the shielding effectiveness of composite structures is presented. The MTL results are compared with the results obtained by another numerical technique. The new model is characterised by simplicity and accuracy and provides an opportunity for easy extension to laminated composite structures     

An electromagnetic model for multiconductor connectors

An electromagnetic model for the response of multiconductor connectors is presented. The model is based on the canonical problem of the electromagnetic response of a thin circumferential slot in the shield of a cylindrical multiconductor transmission line (MTL). The problem is formulated for a shielded MTL of arbitrary cross section with impressed sources driving the interior of the MTL. The problem of interior-to-exterior coupling is solved by treating the slot as a thick aperture in the shield. The equivalence principle is used to divide the original problem into three separate parts. Two coupled integral equations are obtained for the equivalent surface magnetic currents, which are solved by the method of moments, and equivalent networks are presented. The equivalent networks consist of three generalized admittances, one of which is interpreted in terms of a connector admittance     

FDTD analysis of lossy, multiconductor transmission linesterminated in arbitrary loads

A hybrid method is presented for incorporating general terminations into the solution of lossy multiconductor transmission lines (MTLs). The terminations are characterized by a state-variable formulation which allows a general characterization of dynamic as well as nonlinear elements in the termination networks. The method combines the second-order accuracy of the finite difference-time domain (FDTD) algorithm for the MTL with the absolutely stable, backward Euler discretization of the state-variable representations of the termination networks. A compact matrix formulation of the recursion relations at the interface between the MTL and the termination networks allows a straightforward coding of the algorithm. Skin effect losses of the line conductors as well as the effect of an incident field are easily incorporated into the algorithm. Several numerical examples are given which contain dynamic and nonlinear elements in the terminations. These examples demonstrate the validity of the method and show that the temporal and spatial step sizes can be maximized, thereby minimizing the computational burden     

A new current-mode computational analog block free from the body-effect

In this paper, a new computational/configurable analog block (CAB) is presented based on MOS translinear (MTL) for current-mode nonlinear computation. The proposed CAB architecture consists of three main structures: a new MTL cell, NMOS-PMOS arrays, and two local switch networks. As the new trait, it benefits from an effective compensation technique that extensively minimizes the error generated by body effect–the most important factor amongst the second-order effects. The second feature is that the MTL cell only with six transistors has enabled the CAB to implement more arithmetic functions. This block is capable of implementing such various nonlinear functions as squaring, inverse function, N-dimensional vector summation, full-wave rectifier, four-quadrant multiplier/divider, two-quadrant square-root, and exponential functions. The proposed CAB is simulated with CADENCE and HSPICE software in 0.18 μm TSMC CMOS technology at 1.8 V supply voltage. Most importantly, Post-layout plus Monte Carlo, corner case, and temperature variation simulations are performed to investigate its robust performance in the presence of PVT fabrication non-idealities. Functionality and flexibility of the proposed CAB make it suitable for the core block of Field-Programmable Analog Array (FPAA) ICs and signal processing applications.     

Generalized Form of Telegrapher's Equations for the Electromagnetic Field Coupling to Buried Wires of Finite Length

In this paper, a generalized form of telegrapher's equations for electromagnetic field coupling to buried wires is derived. The presented approach is based on thin-wire antenna theory. The effect of a dissipative half-space is taken into account via the reflection/transmission coefficient approximation. The conductor losses can be taken into account via the surface impedance per unit length. The derived equations are treated numerically via the Galerkin–Bubnov indirect boundary element method. Numerical results are presented for induced current along the wire, and compared with transmission-line (TL) and modified TL (MTL) approximations, respectively, for the case of perfectly conducting electrode buried in a lossy medium. It is shown that the TL and MTL approximations can result in an inaccurate induced current distribution along the conductor at HFs and for shorter electrode lengths, respectively.      

Admittance calculation of a slot in the shield of a multiconductortransmission line

The admittance calculation for a narrow slot in the conducting shield of a multiconductor transmission line (MTL) is presented. An approximate calculation is given for the admittance seen looking into a slot in the shield of a multiconductor transmission line when a uniform magnetic current is placed over the slot. The calculation presented is approximate in that only the transmission line mode is used in the calculation. All higher-order waveguide modes are neglected. This allows the magnetic current to be replaced by a point voltage source at the slot location. The admittance calculation then corresponds to calculating the driving point admittance of a point voltage source located in the shield of an MTL     

Modeling of striplines between a power and a ground plane

In this paper, a stripline model is presented for coupled signal lines routed between a power and a ground plane based on multiconductor transmission line (MTL) theory. Through a suitable diagonalization of the MTL equations for striplines, the transverse electromagnetic (TEM) parallel-plate mode is decoupled from the stripline mode. In this way, stripline models that are obtained assuming ideal planes at ground potential can be extended to take into account the nonideal behavior of the planes. The presented model is applied to represent mode conversion due to vias, holes in the reference planes, and terminations of the stripline. Influence of inhomogeneous media is discussed.     

稀疏共形阵列天线方向图综合

提出一种基于多任务学习的共形阵列天线稀疏优化方法.该方法在考虑单元方向图的全局旋转变换和单元极化状态差异的情况下,建立了共形阵列天线导向矢量模型,结合多任务学习框架,以均匀分布共形阵列天线同一平面上阵元的方向图作为目标任务进行学习,通过稀疏向量支撑区的识别,将欠定的阵列流形矩阵方程转换为超定的特征矩阵方程进行求解,在实现阵列方向图逼近的前提下,建立了共形阵列天线阵元激励与位置联合稀疏优化的多任务学习模型.通过分块坐标下降法对稀布共形阵列天线多任务学习模型进行求解,实现了共形阵列天线的稀疏优化布阵.理论分析与实验仿真证明,该方法能有效减少共形阵的单元数量,简化共形阵列天线结构,获得与均匀分布的共形阵列天线性能一致的天线方向图,解决了稀疏共形阵列天线方向图综合优化设计难题.     

Computer aided analysis and design of MOS translinear circuits operating in strong inversion

Recently, it was proposed to generalize the well-known translinear circuit principle in such a way that it also applies to MOS transistors operated in strong inversion. In this paper, the MOS translinear (MTL) principle will be briefly reviewed. A graphical analysis method for MTL-circuits is presented, which can also be applied to bipolar translinear circuits. This graphical method was implemented in a computer program, which is now used as an interactive design tool to implement nonlinear signal processing functions by MTL circuits.     

The finite-difference time-domain solution of lossy MTL networkswith nonlinear junctions

We describe a numerical technique to solve lossy multiconductor transmission line (MTL) networks, also known as tube/junction networks, which contain nonlinear lumped circuits in the junctions. The method is based on using a finite-difference technique to solve the time-domain MTL equations on the tubes, as well as the modified nodal analysis (MNA) formulation of the nonlinear lumped circuits in the junctions. The important consideration is the interface between the MTL and MNA regimes. This interface is accomplished via the first and last finite-difference current/voltage pair on each MTL of the network and, except for this, the two regimes are solved independently of each other. The advantage of the FDTD method is that the MTL equations may contain distributed source terms representing the coupling with an external field. We apply the method to previously published examples of multiconductor networks solved by other numerical methods, and the results agree exceptionally well. The case of an externally coupled field is also considered     

Frequency-domain upper bounds for signals on a multiconductor transmission line behind an aperture

This paper develops a technique for bounding the maximum voltages and currents at terminations of a muiticonductor transmission line (MTL) located behind an aperture-perforated conducting screen excited by an electromagnetic field in the frequency domain. The electromagnetic field is coupled through a small aperture as the excitation of a multiconductor transmission line behind the aperture. A model is presented in terms of external and internal sources which in turn create traveling waves on the multiconductor transmission line. These traveling waves transfer energy to the terminations. The energy at a termination is translated into voltages and currents from which the upper bounds are determined. These upper bounds are obtained using vector norms and associated matrix norms. The formulation is presented in the frequency domain to obtain useful upper bounds for analysis of multiconductor transmission line geometries with aperture excitation.     

Light coupling characteristics of corrugated quantum-well infrared photodetectors

Corrugated quantum-well infrared photodetectors (C-QWIPs) offer simple detector architectures for large-format infrared focal plane arrays (FPAs). The detector relies on inclined sidewalls to couple normal incident light into the absorbing material. Based on a simplified geometrical-optics (GO) model, this light coupling scheme is expected to be effective with little wavelength dependence. In this work, we apply the modal transmission-line (MTL) modeling technique to study in detail its light coupling characteristics and compare the results with the GO model and experimental data. We find that the results of the GO model agree reasonably well with those of the rigorous MTL model for corrugations with metal cover, and both modeling procedures are consistent with experimental data. In particular, both models predict similar increase in the quantum efficiency /spl eta/ with the size of the corrugations, and both indicate similar limiting /spl eta/ when the corrugation becomes very large. For linear corrugations with thick substrates, the maximum /spl eta/ is about 30%. On the other hand, there are also significant differences between the two models when the effects of phase coherence are important. Since the phase of the radiation is taken into account in the MTL formalism but not in the GO formalism, the MTL model is more generally applicable and is more capable of explaining different detector characteristics. For example, it predicts a smaller /spl eta/ for air or epoxy-covered C-QWIPs because of finite optical transmission through the sharp corners in the corrugations, and it indicates an oscillatory function of /spl eta/ because of the existence of optical fringes. It also reveals the wavelength dependence of the coupling, which becomes more pronounced as the thickness of the substrate layer is reduced.     

Generalized translinear circuit principle

It is shown that a generalized interpretation of the translinear (TL) principle leads quite naturally to an extension to MOS circuits. It is shown that two distinct classes of TL circuits exist, one suitable for bipolar and the other for MOS implementation. The MOS-translinear (MTL) circuit principle is derived and an initial classification of simple MTL circuits is proposed. Some examples are given of MTL circuits synthesizing nonlinear functions     

Time-domain upper bounds for signals on a multiconductor transmission line behind an aperture

A technique for bounding the maximum voltages at terminations of a multiconductor transmission line (MTL) located behind an aperture-perforated conducting screen excited by an electromagnetic field in the time domain is developed. The electromagnetic field is coupled through a small aperture as the excitation of a multiconduetor transmission line behind the aperture. A model is presented in terms of traveling waves and multiple refleetion phenomenon. These traveling waves transfer energy to the terminations. The energy at a terminatian is translated into voltages from which the upper bounds are determined. The upper bounds are obtained using vector norms and associated matrix norms.     

External field coupling to MTL networks with nonlinear junctions:numerical modeling and experimental validation

The problem of predicting the voltages and currents induced on a printed circuit multiconductor transmission line (MTL) network by an impinging transient plane wave electromagnetic field is considered. The MTL network contains nonlinear circuit elements and test cases with various dielectric substrates are examined. Numerical predictions based on quasi-TEM models of the MTL and modified nodal analysis (MNA) models of the lumped element junctions are compared to experimental results obtained in the time domain using a GTEM cell. As has been done in the past, the effect of the incident plane wave is introduced as forcing functions in the MTL equations. The primary goal of this paper is to quantify the accuracy of the various commonly used quasi-TEM mathematical time-domain models. It is shown that when modeling the forcing function terms, it is important to take into account the perturbation of the incident plane wave due to the dielectric substrate. (The experimental-numerical comparisons herein are shown for the case of end-fire illumination since it best demonstrates this point.) Neglecting the dielectric effect on the incident transient pulse, even for substrates with low dielectric constant, produces poor results