Memory cross Volterra model for Doherty power amplifier with group delay mismatch

Abstract

A Memory Cross Volterra model for Doherty power amplifiers (PA) with delay mismatch is presented in this letter. During the design process of Doherty power amplifier, gain, efficiency and operation bandwidth are mostly considered. Delay mismatch is difficult to avoid in this kind of dual-path circuit, which reduces the modeling performance of traditional behavioral models. The proposed Memory Cross Volterra Model (MCVM) is derived from the combination of three memory polynomial equations with delay mismatch. Simulation results show that the proposed MCVM has about 10 dB improvement in Normalized Mean Square Error (NMSE) compared to Generalized Memory Polynomial (GMP) with the same model complexity level as GMP. In a measurement experiment, a Doherty PA is tested at 3.45 GHz with 20 MHz LTE signal. Compared with GMP, the proposed MCVM has a maximum 2.5 dB improvement in Adjacent Chanel Power Ratio (ACPR), and the inverse modeling Normalized Mean Square Error (NMSE) is improved from -41.7 to -44.3.