7 GHz MMIC GaN Doherty Power Amplifier With 47% Efficiency at 7 dB Output Back-Off

Design and characterization of a 7 GHz MMIC GaN Doherty Power Amplifier on TriQuint technology are presented. To the best of the authors' knowledge, the present circuit, suitable for C-band point-to-point backhaul applications, represents the first example of a working MMIC GaN Doherty. Large signal measurements, averaged over 16 MMICs, exhibited power gain of 10 dB, saturated output power in excess of 37 dBm (3 dB gain compression), together with drain efficiency of 47%, at 7 dB of output back-off, and higher than 35% in a 350 MHz band. Two-tone characterization has shown a carrier to 3rd order intermodulation ratio higher than 25 dB in the Doherty region.

I Introduction

The microwave backhaul system architectures, handling the link between base-stations and mobile switching nodes, represent today an effective alternative to solutions based on wired or optical fiber hard connections, for lower maintenance, simpler installation, and wide range coverage [1]. In this framework, the power amplifier is the key element of the entire front-end transmitter chain, in terms of energy and thermal budgets, size, reliability, and consequently cost.