Multi-octave linear efficient GaN power amplifier

Abstract

GaN RF technology has continued to demonstrate state-of-the-art power, efficiency, linearity, and low-noise performance in RF and mm-wave band. Here, we report on a multi-octave (100 MHz–8 GHz), linear nonuniform distributed amplifier (NDPA) in a MMIC architecture using scaled 120-nm short-gate-length GaN HEMTs. The linear NDPAs were built with six sections in a nonuniform distributed amplifier approach, where each cell consists of main and gm3 cells. The small signal gain was >10 dB over the band, with saturated CW output power of ∼35 dBm at Vdd = 17 V. The PAE improved by 7%–10% within the band compared to the previous NDPA with 150-nm gate-length GaN FETs. Based on two-tone testing, the linear NDPA showed improved OIP3 of ∼50 dBm, compared to OIP3 of 42 dBm for the NDPA without linearization. Under QPSK LTE waveform, the ACPR was improved by ∼10 dBc at average output power of 23 dBm, without digital pre-distortion.