Broadband Doherty Power Amplifier with baseband impedance control for concurrent application

Abstract

Traditionally, the concurrent power amplifier (PA) works at two fixed frequency point, limiting its application. Indeed, broadband PA with flexible concurrent frequency point is highly expected. This paper presents a broadband Doherty PA (DPA) with base-band impedance control for concurrent application. The bias network is carefully designed to control base-band impedance over a wide bandwidth, enabling flexible concurrent frequency adjustment in the DPA operation frequency band. Simultaneously, the basic theory of a concurrent class-B PA is analyzed. Then, the efficiency response of a concurrent DPA is derived. As a validation, this paper implements a 1.8–2.2 GHz broadband DPA for concurrent application. Under a continuous-wave (CW) signal excitation, the fabricated DPA achieves a maximum output power of 43.4–44.1 dBm, a saturation drain efficiency (DE) of 55.4%–67% and a 6 dB back-off DE of 47%–54% over 1.8–2.2 GHz. Moreover, under the excitation of an equal-amplitude two-tone signal, the fabricated DPA achieves a maximum concurrent output power of 40.7–42.2 dBm over tone spacing of 20–400 MHz, the measured back-off concurrent DE changes from 44% to 48% and the saturation concurrent DE changes from 55% to 68.5% over tone spacing of 20–400 MHz.