Class-F−1 Asymmetric Doherty Power Amplifier Integrated Slot Antenna Array With High Efficiency and Large Back-Off Range

This research proposes an asymmetric Doherty power amplifier integrated active antenna (ADPAIA) with high efficiency and large back-off range, integrating a Class-F⁻¹ gallium nitride (GaN) monolithic microwave integrated circuit (MMIC) Doherty power amplifier (DPA) with an on PCB stub-loaded wide-slot antenna array (SLSAA). In this work, the phase difference and current ratio between the carrier and peaking amplifiers are meticulously designed. These parameters play a crucial role in determining both the impedance matrix of the DPA’s output network and its back-off range. Through fine-tuning these parameters, the fundamental impedance of the carrier and peaking amplifiers in the DPA at both peak power and output power back-off (OPBO) states can directly match the precisely tailored input impedance of the SLSAA, enabling a large back-off range. Unlike conventional DPA integrated antennas, where the active load modulation of the DPA is achieved through the output matching network (OMN) and power combiner network (PCN) of the DPA, the active load modulation in the ADPAIA is realized through spatial coupling of the SLSAA. Moreover, the harmonic impedances of the DPA are modulated by optimizing the dimensions of the SLSAA’s stubs. Consequently, the DPA’s OMN, PCN, and the harmonic control network (HCN), which are essential for traditional Class-F⁻¹ DPAs’ integrated antennas but typically introduce unavoidable insertion loss, are eliminated for the first time. The fabricated ADPAIA demonstrates a maximum power-added efficiency (PAE) of 47.8% at peak power and 44.5% at 8-dB OPBO under continuous-wave signal testing across 4.5–4.9 GHz. These PAE results, along with the power back-off range, outperform the performance of previously reported integrated DPA antennas, which are essential for modern wireless communications.