Two-stage regenerative microwave amplifiers with reduced nonlinear distortions

Characteristics of reflection type regenerative microwave amplifiers using Gunn-effect diodes, IMPATT diodes, or tunnel diodes with reduced third order intermodulation were calculated. A sinusoidal voltage across the nonlinear element of negative conductance diodes or a sinusoidal current through the nonlinear element of negative resistance diodes were assumed. The saturation power, equal to the nominal power of the signal source, at which the power transmission coefficient differs by 1 dB from the small signal power transmission coefficient, is calculated first for the simplest case of an amplifier which consists of an ideal circulator and an active nonlinear element, with the nonlinearity and for an input signal which consists of a fundamental component and a third harmonic only. Two real nonlinear elements with a soft oscillation characteristic are considered. It is revealed that the saturation power is most effectively increased by staging. It is shown that the power of third order intermodulation components does not depend on the matching circuit and that the power transmission coefficient varies only slightly with varying gain distribution over amplifier stages.