A 3.4–5.4-GHz Highly Efficient GaN Balanced Power Amplifier With Selectable Output Port for Polarization Diversity Application

A high-efficiency broadband balanced power amplifier (BPA) with selectable ports for polarization diversity application is proposed in this letter. The proposed design utilizes two Lange couplers for power combining and a transformer that can achieve 0° phase shift and −180° phase shift switching for port selection. By using the proposed architecture, the port switching function can be integrated before the main PA, eliminating the traditional single pole double switch (SPDT) after the main PA for polarization diversity and thereby increasing overall system power efficiency. To demonstrate the idea, a PA with a switchable output port was designed and fabricated using the 120-nm GaN process. Measurement results show that the operating frequency covers 3.4–5.4 GHz, with power added efficiency (PAE) of 24.8%–40.3% and a saturated output power of 36–37.6 dBm. The overall area of the chip is $2\times 4.1$ mm². The proposed design is suitable for a dual-port polarization antenna system.