Symbolic solution of the multiconductor transmission-line equationsfor lines containing shielded wires

The multiconductor transmission line equations that characterize crosstalk in a multiconductor transmission line containing a shielded wire are solved in symbolic form, that is, the resulting crosstalk voltages are determined in terms of symbols rather than numerical values. The resulting solutions show the frequency range for which the widely used, low-frequency, inductive-capacitive coupling model is a valid representation. The solution shows that the inductive-capacitive coupling model is an adequate characterization of crosstalk for lines that are electrically short and whose termination impedances do not differ substantially from the characteristic impedances of the lines that are involved. For lines whose termination impedances differ drastically from the line characteristic impedances, the inductive-capacitive coupling model is valid only for frequencies where the line is extremely short, electrically. For higher frequencies of excitation, the model may give predictions that are substantially below the true crosstalk even for frequencies where the line is electrically short     

Extension of Chang-Chang's method to analysis of generalised multilayer and multiconductor transmission-line system

The characterisation of the capacitance matrix of a multilayer and multiconductor transmission-line system is very important in the development of microwave integrated circuits. Many practical multilayer and multiconductor configurations are just special cases of the general configuration described in the letter. The method presented is based on the variational principle. The determination of the capacitance matrix of a generalised N-layer and N-strip transmission-line system is programmable on a digital computer. It should be realised that the transverse-transmission-line concept does indeed make the application of the variational analysis to a multilayer and multiconductor system a relatively simple task.     

Evolutionary generation of 3-D line-segment circuits with a broadside-coupled multiconductor transmission-line model

Evolutionary generation of three-dimensional microwave line-segment circuits embedded in a multilayer structure is presented. Connections of the line segments and their lengths are expressed by sets of parameters, which are evolutionarily optimized by the genetic algorithms. Practical optimization time is achieved by introducing models of broadside-coupled multiconductor transmission lines instead of full-wave electromagnetic (EM) calculations. The scattering parameters of the models are connected with the scattering parameters of vias, and are synthesized into that of the whole circuit. Using line segments, we can obtain not only small components for limited-space applications, but also large components for wide-band frequency specifications without increasing computational complexity. Two bandpass filters and a bandstop filter were designed and tested by an EM simulator. The bandpass filters were also fabricated and measured. The results validated our proposing procedure.     

Full-wave analysis of complicated transmission-line circuits using wire models

Three existing wire models based on the method of moments are used to analyze a transmission-line circuit. Simulation results show that the wire model where the current is assumed to flow along the axis and the testing is on the whole surface (around 2/spl pi/) has the best performance when two wires are close. However, this model is still inaccurate when two wires are very close, which is the case in computer chip and circuit problems. We then develop a new wire model that is valid for many cases. Using the new wire model, complicated transmission-line circuits can be accurately analyzed and simulated. Many numerical simulations are given to test the validity of the new model.     

FDTD analysis and measurement of aperture antennas based on thetriplate transmission-line structure

First, two aperture antennas designated as P-type and C-type antennas are analyzed using the finite-difference time-domain (FDTD) method. Each antenna is made of a triplate transmission line (TTL). A square aperture is cut out of the top plate of the TTL for both antennas to allow radiation. The bottom of the TTL is a planar plate for the P-type antenna and a plate with a hollow cavity for the C-type antenna. The power flow is expressed using Poynting vectors. It is revealed that parallel-plate mode power in the TTL is lower in the C-type antenna, compared with that in the P-type antenna. Second, an array antenna composed of two C-type elements is analyzed. The Poynting vector distribution in the aperture is found to remain almost unchanged when the element spacing is varied. The input impedance of the array antenna converges at an element spacing of approximately 0.9 wavelength. The theoretical radiation patterns are in good agreement with measured data     

Deterministic modeling of the (shielded) outdoor power line channel based on the multiconductor transmission line equations

In this paper, a complete methodology is proposed for the deterministic modeling of the channel transfer functions associated with underground power line access networks, in the light of the Multiconductor Transmission Line Theory. Some multiconductor power line cables are analyzed in detail, and their fundamental propagation characteristics (definition of eigenmodes, phase velocity, characteristic impedance, lineic attenuation) are related to the geometry of the conductors and the material properties. A multidimensional scattering matrix formalism is then introduced to perform an accurate analysis of the global power line network including multiconductor cable segments, derivation points, and termination loads. An illustrative example of a power line access network with three types of cables (with different numbers of conductors), 20 derivations, and five remote terminals, is finally proposed.     

Time-domain vector-potential analysis of transmission-line problems

A time-domain vector-potential (TDVP) approach for the analysis of transient electromagnetic fields is proposed in this paper. The field is analyzed by the magnetic VP for which the wave equation is solved by a finite-difference (FD) scheme. The feasibility of the method has been shown by simulations of several transmission-line problems. The results have been compared with reported data obtained by the conventional finite-difference time-domain (FDTD) method, empirical formulas, and measurements. The proposed approach is not inferior to the FDTD method in terms of generality and memory requirements. At the same time, a reduction of central processing unit (CPU) time is achieved because only three scalar wave equations are solved instead of the six Maxwell equations for all field components. It has also been shown that there are certain structures where the components of the magnetic VP are decoupled, which implies the possibility for a consecutive algorithm with reduced memory requirements     

Sensitivity analysis of a multiconductor transmission line

In this paper, the theory for the sensitivity analysis of a multiconductor line is described, and the sensitivities of the receivingend voltage and power with respect to the various line parameters have been evaluated.     

Frequency-dependent analysis of a shielded microstrip stepdiscontinuity using an efficient mode-matching technique

The basic concepts of the mode-matching technique are used to formulate the boundary condition problem associated with the microstrip step discontinuity problem. The fields on both sides of a discontinuity are expanded in terms of the normal hybrid modes of the shielded microstrip line. The properties of these hybrid modes are determined by applying a previously developed analytical approach due to R. Mittra and T. Itoh (1971) using singular-integral-equation techniques. In addition to propagating modes, higher-order modes are also taken into account. The higher-order modes are evanescent-type waves. The propagation constants of the evanescent waves in general are found to be complex numbers. A mode-matching procedure is developed to determine the reflection and transmission coefficients of the discontinuity. The use of two types of products to treat the boundary conditions for the continuity of the tangential electric and magnetic fields results in a highly efficient and numerically stable solution. Numerical results are computed for several step discontinuities and the results are compared with previously published data     

Efficient sensitivity analysis of transmission-line networks usingmodel-reduction techniques

An efficient algorithm, based on congruent transformation and model reduction, is proposed for evaluation of frequency- and time-domain sensitivity of large linear networks containing lossy coupled transmission lines. The sensitivity of the voltage and current waveforms can be calculated with respect to lumped components and parameters of transmission lines. The algorithm is based on projecting the adjoint network equations on a reduced-order subspace that preserves the circuit moments. The proposed algorithm provides a significant decrease in the computational expense for sensitivity analysis     

Calculation of transients on unsymmetrical multiconductor line systems using the graphical method

The `graphical method? previously discussed for transient calculation in single-conductor transmission-line systems is generalised for unsymmetrical multiconductor lines having N conductors. The solution equations are expressed in a form suitable for digital programming.     

Linear transmission-line model analysis of arbitrary-shape patch antennas

A quasi-TEM lossy transmission-line model is used to express the radiation admittance of an arbitrary-shape symmetrical patch antenna which is linearly polarised. The then retical admittance is obtained from the solution of a Riccati differential general equation.     

宽带传输线变压器的分析与设计

研究了变换比为1：n^2(n为整数）的宽频带传输线变压器,给出了考虑线圈互耦的等效电路模型,分析了其阻抗变换特性。然后在此基础上,通过实验调试,研制了工作频带为30MHz-450MHz、变换比为1：1．6的传输线变压器,总结出设计任意变换比传输线变压器的一些结论。     

Conformal mapping analysis of shielded striplines

The method of conformal mapping is used to modify shielded stripline configurations into that of a strip over an infinite ground plane. Results known for the latter structure allow the evaluation of the stripline parameters. This formulation applies to narrow strips located both symmetrically and asymmetrically inside the shielding.     

Practical limitations of subwavelength resolution using negative-refractive-index transmission-line lenses

Previously, we have demonstrated both analytically and experimentally subwavelength imaging using a negative-refractive-index lens made of a periodically L, C loaded transmission line (TL) network. This loaded transmission line network has been referred to as the dual TL lens. Here, we consider the limitations on subwavelength imaging imposed by impedance mismatches and the component losses of a practical dual TL lens. Simple expressions for estimating the resolving capability of a dual TL lens are given. It is found that the resolution enhancement of the dual lens is proportional to the quality factor of the series loading capacitors divided by the electrical thickness of the lens. The effective material parameters of the dual TL lens are also derived so that these expressions can be directly related to those of previous studies considering uniform and isotropic left-handed lenses. Finally, the resolving capability of an experimental lens that achieves subwavelength imaging is theoretically predicted. These theoretical predictions are then directly compared to previously reported experimental results.     

Dispersion analysis of a microstrip-based negative refractive index periodic structure

We present the complete band structure of a negative refractive index metamaterial based on the concept of dual transmission lines. The metamaterial is a two-dimensional (2-D) microstrip periodic structure that has cell dimensions much smaller than the wavelength of operation. It can therefore be considered as an effective medium. First, the dispersion characteristics of the metamaterial are explained by way of a 2-D loaded transmission line representation. Subsequently, full-wave analysis is utilized to reveal additional modes that can be excited in the metamaterial.     

Linear transmission-line model analysis of a circular patch antenna

Using a linear transmission-line model analysis we calculate the radiation admittance in the particular case of the circular patch antenna. Theoretical bandwidth, radiation admittance and resonance frequency are compared successfully with experimental results given by other authors.     

Efficient transient analysis of nonlinearly loaded low-loss multiconductor interconnects

The combined time- and frequency-domain analysis of nonlinearly loaded low-loss interconnects is addressed. We show that a variety of interconnects commonly employed in different technological applications are characterized by transfer functions, whose impulse responses have a fast initial-time structure (due to the skin effect) and a slow long-time part (due to ohmic losses). The dependence of the impulse response structure on the line parameters is discussed, along with the exact analytical solutions valid for the skin effect and ohmic losses, separately. A piecewise linear approximation of the transient functions with nonuniform sampling is proposed as an effective method to obtain high accuracy at low computational costs. Various numerical examples are used to validate the effectiveness of the proposed representation, and to show that a matched characterization of the line must be adopted in order to avoid numerical artifacts.     

Adaptive transient solution of nonuniform multiconductor transmission lines using wavelets

This paper presents a highly adaptive algorithm for the transient simulation of nonuniform interconnects loaded with arbitrary nonlinear and dynamic terminations. The discretization of the governing equations is obtained through a weak formulation using biorthogonal wavelet bases as trial and test functions. It is shown how the multiresolution properties of wavelets lead to very sparse approximations of the voltages and currents in typical transient analyzes. A simple yet effective time-space adaptive algorithm capable of selecting the minimal number of unknowns at each time iteration is described. Numerical results show the high degree of adaptivity of the proposed scheme.     

Efficient sensitivity analysis of lossy multiconductor transmissionlines with nonlinear terminations

An efficient approach for sensitivity analysis of lossy multiconductor transmission lines in the presence of nonlinear terminations is described. Sensitivity information is extracted using the recently developed closed-form matrix-rational approximation of the distributed transmission-line model. The method enables sensitivity analysis of interconnect structures with respect to both electrical and physical parameters. An important advantage of the proposed approach is that the derivatives of the modified nodal admittance matrices with respect to per-unit-length parameters are obtained analytically