A compact, 42% PAE, two-stage, LDMOS Doherty PA Module for Massive MIMO applications

Massive MIMO systems for pre-5G and 5G applications have necessitated the development of low power (2-5W average) high efficiency PAs due to the need for multiple PA elements to form a 64, 128 or 256 element array base station system. Such requirements pose several challenges such as the need for high efficiency, linearizability with simple digital predistortion systems, low cost and small form factors. In this paper, we discuss a novel technique for the miniaturization of a fully-integrated, low-cost LDMOS Doherty Power amplifier using ABCD matrix equivalents for the matching networks. A small form factor 50-Ohm in-out Doherty PA is designed for the 2.5-2.7GHz band and its performance is discussed in the context of a low-complexity DPD system with very few coefficients. The PA achieves a PAE of 42% with a gain of 32dB and corrects to -55dBc with a 60MHz (3x20MHz) LTE signal.