A new adaptive double envelope feedback (ADEF) linearizer for solid state power amplifiers

A new adaptive double envelope feedback (ADEF) linearizer using a voltage-controlled phase-shifter for predistortion purpose and a dynamic gate bias for gain stabilization purpose has been developed and implemented on a two-watt MESFET amplifier. A two-tone test around 1.6 GHz shows average in-band intermodulation product below -40 dBc up to saturation with a power-added efficiency of 40% at the 1-dB compression point. Validation of the adaptive features of the ADEF technique is carried out with respect to carrier frequency, temperature, two-tone amplitude offset and spacing. In addition, a new formula, which directly relates the third order intermodulation level to the AM/AM and AM/PM distortion coefficients of solid state nonlinear amplifiers is proposed and its accuracy is assessed using both simulation and experimental results