Simple, low-cost, subsystem fabrication

We have successfully developed a simple and low-cost 1.9-GHz, 25-W power amplifier by using only one prematched 50-mm PHEMT with external matching circuits on a FR-4 PCB. As the output stage integrated with other driver stages and dc control circuits, a completed four-stage power-amplifier subsystem is also demonstrated. When operating at 38.5-dBm output power with π/4-DQPSK signal, the proposed power amplifier subsystem shows low distortion, with better than 75-dBc ACPR (adjacent-channel leakage power ratio) at 600 kHz and 79-dBc ACPR at 900 kHz offset from the center frequency, and is suitable for PHS 500-mW base-station applications.