Abstract: A high-performance power amplifier-antenna integrated circuit with circularly polarized radiation characteristics is designed. By directly optimizing the input impedance of the circularly polarized antenna, it is directly integrated with the power amplifier circuit without the output matching network. This seamless integration not only decreases insertion loss and mismatch loss, but also effectively reduces circuit size and improves overall performance. The circularly polarized antenna is composed of a rectangular patch and a modified ground plane. The 3 dB axial ratio bandwidth of the antenna is enhanced by adding vertical stubs and cutting horizontal slots in the ground plane. For verification, an integrated circuit prototype operating at 3. 4 GHz~ 3. 6 GHz is designed, fabricated, and measured. The experimental results show that the power-added efficiency (PAE) of the power amplifier-circularly polarized antenna integrated circuit exceeds 60% in the operating frequency band, and the 3 dB axial ratio bandwidth reaches 320 MHz (9. 1% for the center frequency of 3 500 MHz). Compared with the traditional cascaded design, the PAE is im-proved by 8. 5%, and the 3 dB axial ratio bandwidth is also improved.