Power amplifier linearization using IF feedback

A narrowband feedback technique for linearizing power amplifiers is presented. The technique uses frequency conversions, thus allowing loop compensation and added loop gain to be implemented at the intermediate frequency (IF). An analysis is presented which allows assessment of the applicability of the technique and which shows the performance advantages of using a two-pole loop compensation filter. When applied to a 450-MHz power amplifier with a delay of 70 ns, the technique suppressed intermodulation products at +or-500 kHz by 12 dB with the amplifier driven to within 5 dB of its 1-dB compression point.<
>