Intermodulation Analysis of Microwave Mixers by a Sparse-Matrix Method Coupled with the Piecewise Harmonic-Balance Technique

The analysis of intermodulation distortion in microwave mixers by the Newton-iteration based harmonic-balance technique may lead to numerical problems of unmanageable size, especially for modern multiple-device topologies. The paper describes a sparse-matrix approach providing an effective solution to this shortcoming. Selected entries of the Jacobian matrix are set to zero according to some physical criterion, which leads to a sparse matrix with a predetermined pattern of nonzeroes. A specially developed sparse-system solver may then be applied with optimum efficiency. Both memory storage and CPU time are reduced by two orders of magnitude in the analysis of a typical distributed device.