Reduction of intermodulation distortion in microwave active bandpass filters - Theory and experiments

This paper examines, both theoretically and experimentally, the dependency of the third-order intermodulation (IM) distortion and power saturation upo n circuit and device parameters of an active bandpass filter using negative -resistance compensation. Nonlinear analysis is performed by means of the V olterra series formulation. We show that the IM distortion can be reduced b y several orders of magnitude with suitable choice of external gate-source and feedback capacitance values. Measured performances of some 900-MHz expe rimental MESFET bandpass filters are presented.