Model reduction of time-varying linear systems using approximate multipoint Krylov-subspace projectors

A method is presented for model reduction of systems described by time varying differential algebraic equations. This method allows automated extraction of reduced models for nonlinear RF blocks, such as mixers and filters, that have a near linear signal path but may contain strongly nonlinear time varying components. The models have the accuracy of a transistor level nonlinear simulation, but are very compact and so can be used in system level simulation and design. The model reduction procedure is based on a multipoint rational approximation algorithm formed by orthogonal projection of the original time varying linear system into an approximate Krylov subspace. The models obtained from the approximate Krylov subspace projector can be obtained much more easily than the exact projectors but show negligible difference in accuracy.