Nonlinear system performance of shared amplifiers based on 3-way microstrip phase combiners

A nonlinear system analysis of a medium power 3-way shared amplifier is presented. It includes a first time practical verification of the new concept using a medium power setup at a design frequency of 1.9 GHz with an operational bandwidth of more than 300 MHz. The splitters and combiners are based on a novel, size-reduced planar multilayer microstrip implementation of a previously proposed coaxial 3-way phase combiner. The shared amplifier provides a gain of 12.85 dB in linear mode with excellent sector isolation of more than 30 dB. In large signal operation, a 5dB improvement in 1 dB-compression point and odd-order intercept points could be achieved compared to a single amplifier. We discovered a unique feature of coherently eliminating 3rd-order intermodulation products using only two channels of this setup. This effect is explained by theory and validated by measurements.