Designing a Doherty Power Amplifier Without Offset Compensation Lines
Keywords:
Doherty power, offset compensation lines, AM/PM , circuit analysisAbstract
This work presents the equivalent electrical circuit (EEC) analysis of the 2-way Doherty Power Amplifier (DPA). For this purpose, the sub-amplifiers used in the 2-way DPA are modeled using real voltage sources instead of ideal sources. For the first time, the general voltage and current equations for each node of the EEC are determined using circuit theory and transmission line equations. The analysis results provide the fundamentals for the empirical practices carried out in other works to tune the 2-way DPA efficiency response. This analysis allows us to examine the impact that the auxiliary sub-amplifier bias voltage has on the efficiency of the 2-way DPA, suggesting the use of the phase-to-amplitude distortion (AM-PM) of the auxiliary sub-amplifier to eliminate the compensation lines that are commonly implemented arbitrarily in the 2-way DPA, whose objective is to synchronize the output signals of the sub-amplifiers. The experimental data of a 20 W (43 dBm) 2-way DPA designed and fabricated for a central frequency of 1.875 GHz with GaN transistors validate the proposed idea, resulting in a compact design and a significantly reduced design time.
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References
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