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A numerical method using impulse analysis of a transmission-line matrix is introduced and used to obtain wave-impedance values in a waveguide. The method is demonstrated by applying it to the scattering caused by a waveguide bifurcation.

SUMMARYThis paper describes a simple explicit and unconditionally stable numerical routine for the solution of the diffusion equation using a transmission-line modelling (TLM) method. The paper also shows that the explicit finite difference routine and the implicit Crank-Nicolson routine may be expressed as the exact solution of certain transmission-line models. Using these models a technique for comparing the accuracy and stability of numerical routines is developed and a detailed comparison of the new TLM methods and the well established methods is made.

affected by the overlap region between the I, and Vce. Obviously, the overlap between V,, and I, can be observed by introducing ESR. All in all, the two results are quite close. CONCLUSIONSIn this article, a simple numerical technique is described to model a reactively loaded power amplifier. The adding of an ESR can demonstrate its effect on the collector efficiency, which is particularly important in high-frequency operation. In addition, TLM can control the distributed circuit parameters by the time step size, as mentioned in Eqs. (3) and (6). The advantages of using TLM and ESR are that only a simple algorithm is required, computational time is short because the procedure for the inverse Laplace transform of the matrix equation is not required, the overlap zone of I , and V,, can be easily observed, and the procedure for optimization can be easily developed. REFERENCES 1.ABSTRACT Plots for optimizing the performance of LNA are presented here. From the .study of the interaction between the inputloutput stability and the conjugate-match conditions, four modified stability circles which are designated as matching circles are analytically developed for the inputlouptui networks. The available matching area is specified by using the modified determinations of the stability criteria. KEY TERMSRandom rough surface scattering, banded matrix iterative approach, Monte Carlo simulations ABSTRACT A banded matrix iterative approach is applied to study scattering of a TM incident wave from a perfectly conducting one-dimensional random rough surface. It is much faster than the full matrix inversion approach. When compared to the Kirchoff iterative approach, it is of comparable CPU time, is more accurate, and works for cases when the Kirchoff iteration fails. 0 1993 John Wiley & Sons, Inc.

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