A Simplified Transistor-Based Analog Predistorter for a GaN Power Amplifier

A simplified transistor-based analog predistorter (APD) is proposed and used to linearize a GaN power amplifier (PA). The proposed APD features simple circuit topology because no additional vector modulator is needed. To demonstrate the new methodology, a GaN power amplifier centered at 2.4 GHz using the proposed APD is implemented and tested. From the measurement results, the output 1-dB gain compression point of the GaN PA with the proposed APD is increased from 35.2 dBm to 38.9 dBm under CW signal, while the efficiency is increased by 8.5%. Two-tone test is also implemented, indicating more than 10 dB third order intermodulation distortions improvement over a wide range of output power levels. For a single-carrier downlink WCDMA signal at 2.4 GHz, the experimental results demonstrate an adjacent channel leakage power ratio reduction of 13 dB.