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.
High frequency digital LSIs usually consist of many subcircuits coupled with multi-conductor interconnects embedded in the substrate. They sometimes cause serious problems of the fault switching operations due to the time-delays, crosstalks, reflections and so on. In order to solve these problems, it is very important to develop a user-friendly simulator for the analysis of LSIs coupled with interconnects. At the reduction algorithm, we first calculate the dominant poles which give the large effects to the transient response, and the corresponding residues are estimated by the least squares method. Thus, the interconnect is replaced by the equivalent circuit realizing the partial fractions.
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