Compact Doherty Power Amplifier–Circularly Polarized Antenna Integration for Phased Arrays

In this communication, a compact Doherty power amplifier–circularly polarized antenna (DPA-CPA) operating at 3.5 GHz is presented for high-efficiency phased arrays. Unlike conventional designs with separate amplifiers and antennas connected via passive matching networks, the proposed DPACPA directly integrates the antenna with the amplifier, eliminating interconnect losses. The antenna provides decoupled control of input impedance and axial ratio (AR), allowing its impedance to be tuned to match the DPA’s two-port output network while maintaining stable circular polarization. Simulations and measurements show that the radiation patterns vary by less than 0.1 dB between saturation and 6-dB back-off. The integrated element achieves drain efficiencies of 67.5% and 51.5% at saturation and 6-dB back-off, respectively. With a compact size, the DPACPA is well suited for integration into planar phased arrays. The simulated beam-scanning performance of the 1×4 array shows a ±50° range with less than 2 dB gain variation and an AR consistently below 3 dB. These results demonstrate a new approach to DPA–CPA integration, offering power-invariant radiation, independent impedance–polarization control, and a compact form factor, which are highly attractive for energy-efficient multi-channel phased array transmitters.