Impact of the Input Baseband Terminations on the Efficiency of Wideband Power Amplifiers Under Concurrent Band Operation

Abstract

This article presents a theoretical explanation of the efficiency degradation in wideband radio frequency power amplifiers (RFPAs) under concurrent dual-band operation that is still visible after eliminating all known causes related to the output matching network (OMN). First, the origin of this degradation, identified by the reduction of the PA's efficiency and linearity, is traced to the input baseband impedance terminations. Then, a theoretical model that describes the phenomenon and qualitatively predicts the efficiency variation under concurrent dual-band operation is presented using a simple model based on two-tone excitation. Finally, the proposed explanation is confirmed by comparing the efficiency performance of two 30-W GaN RFPAs of distinct instantaneous bandwidth determined by different input video-bandwidth terminations, under two-tone and concurrent dual-band operation. This article shows that, in addition to the adequate OMN design, an optimal input baseband impedance profile is also an important design constraint needed to keep the efficiency and linearity performance of RFPAs, for scenarios that require a wide instantaneous bandwidth.

Fully integrated three-way LDMOS Doherty PAs for 1.8–2.2 GHz dual-band and 2.6 GHz m-MIMO 5G applications

“…The two tones spread is also due to the gate envelope impedances that are treated mainly with an external base band decoupling circuit. To further optimize the shapes of IMDs a more powerful gate decoupling network must be implemented, preferably inside the package as in [20,21].…”