Discrete RF power synthesis of OFDM signals with high efficiency at high peak to average power ratios

Abstract

OFDM signals suffer from large peak to average power ratios (PAR.) forcing the RF power amplifier (PA) to operate inefficiently in backoff modes. This problem is hard to solve, especially when the RFPA comprises a single active device. We describe a technique of power synthesis using several discretely combined devices (FET arrays) to enhance RF power efficiency while achieving high PAR, values. We show that by suitably combining phase-switched amplifiers, one can achieve comparable BER performance to normal class-A linear amplifiers. We analyze the effect of phase distortions that arise in large integrated FET arrays, and we quantify the PM-AM effects therein. Simulations in AWGN show that one can achieve BERs comparable to full-precision, linear approaches by using only 4-5 discrete RF synthesis stages in the RFPA module.