SUMMARYWe propose here a Spice-oriented envelope analysis based on the HB (harmonic balance) method, where Fourier coefficients are assumed to be slowly varying. The Fourier expansions of nonlinear devices are executed by MATLAB in the symbolic forms. In this time, the nonlinearities need to be approximated by the polynomial functions. The determining equation of the HB method is formulated as Sine-Cosine circuit in the form of schematic diagram using ABMs (analog behavior models) of Spice. Each sub-circuit corresponding to the higher harmonic component is almost the same circuit topology as the original one and has dynamic elements such as capacitors and inductors. The Sine-Cosine circuit can be solved by the transient analysis of Spice. Thus, our method is rather a symbolic approach in the meaning that the HB determining equation is given by the schematic diagram of Spice. Our method can be easily applied to the analysis of middle order of nonlinear communication circuits such as mixers and amplitude modulators and to the analysis of interesting phenomena in the nonlinear oscillations. After many simulation experiments, the results show that our envelope analysis is about 50 times faster than the direct transient analysis.
In this article, the performance of some communication systems using chaos synchronization is evaluated and compared. The evaluation of bit error rate is done for not ideal communication channel but lossy and noisy one. It is confirmed that a chaos-based communication system has a good performance which may be almost the same compared with conventional analog modulation schemes.
Abstract-The purpose of this brief is that, by an application of the method of characteristics, we analyze chaotic phenomena in Chua's circuit with lossy transmission line. The transmission line is replaced by the equivalent lumped circuit and a time-delayed element so that it can be solved efficiently by the Runge-Kutta method. It is found from numerical experiments that the circuit has complicated and interesting chaotic attractors.
Masayoshi ODA †a) , Nonmember, Yoshihiro YAMAGAMI †b) , Junji KAWATA † †c) , Yoshifumi NISHIO †d) , Members, and Akio USHIDA † †e) , Fellow SUMMARY We propose here a fully Spice-oriented design algorithm of op-amps for attaining the maximum gains under low power consumptions and assigned slew-rates. Our optimization algorithm is based on a well-known steepest descent method combining with nonlinear programming. The algorithm is realized by equivalent RC circuits with ABMs (analog behavior models) of Spice. The gradient direction is decided by the analysis of sensitivity circuits. The optimum parameters can be found at the equilibrium point in the transient response of the RC circuit. Although the optimization time is much faster than the other design tools, the results might be rough because of the simple transistor models. If much better parameter values are required, they can be improved with Spice simulator and/or other tools.
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