Design of Efficient Concurrent Dual-Frequency Doherty Power Amplifier Based on Step Impedance Low-Pass Filter

In view of the peak-to-average power ratio (PAPR) of wireless communication base stations, a Doherty power amplifier with high efficiency maintained at output power back-off (OBO) can effectively solve the problem of low efficiency of the traditional power amplifier at the point of power back-off. In this paper, we propose a method to implement a dual-frequency Doherty power amplifier (DPA) using a step-impedance low-pass filter to improve the bandwidth and efficiency of the DPA at output power back-off (OBO). Step impedance low-pass filters are used to solve the bandwidth limitations in traditional impedance converters and improve the efficiency of Doherty power amplifiers to a certain extent. In order to verify the proposed scheme, an efficient concurrent dual-band Doherty power amplifier operating at 2.0/3.5 GHz is designed and fabricated for the first range 1 (FR1) of 5G applications. In the measured results, the concurrent dual-band DPA achieves a saturated output power of 44 dBm and drain efficiency of 62% with a 6 dB back-off efficiency of 53% at 2.0 GHz and a saturated output power of 43.5 dBm and drain efficiency of 68% with a 6 dB back-off efficiency of 58% at 3.5 GHz.