A circuit solving method for output matching network parameters of Doherty power amplifiers

Abstract

In this paper, all possible numerical solutions are provided when the matching conditions for Doherty power amplifier (DPA) back-off and saturation states are met. Firstly, this article presents an impedance expression of the DPA. Then all circuit parameter solutions can be solved for the load modulation of DPA using this expression. In the process of solving circuit parameters, the impedance matching of the DPA at the saturation level is established through the analysis of the S-parameter matrix. Then by limiting the impedance solution range of DPA at the output power back-off (OBO) level, the circuit parameter solutions that satisfy the specified conditions are meticulously screened. The output matching network of the DPA is designed according to the obtained circuit parameter solutions for broadband operation. To validate the proposed design method, a broadband DPA operating from 1.2 to 2.4 GHz is designed and measured based on the proposed method. Under the continuous wave excitation, the measured drain efficiency at 6 dB OBO level and saturation (SAT) level are 44%–56% and 51%-65.4% from 1.2 to 2.2 GHz, respectively. The peak output power is 45.1–46.3 dBm.