Nonlinear nodal analysis of varactor-tuned microwave filters

A nonlinear nodal analysis method is introduced to study the effects of high input power on varactor-tuned filters. Analysis is performed in the lowpass domain by calculating the nonlinear reactance deviation at each node using an iterative approach and nonlinear filter response is calculated by simple matrix inversion. Comparison of theoretical results with harmonic balance simulations shows good agreement. The proposed method has potential application in the design of highly linear tunable filters.