An Efficiency-Enhanced GaN MMIC Nonuniform Distributed Power Amplifier Using a Modified Gate Line Structure

This article introduces a novel four-cell nonuniform distributed power amplifier (NDPA) structure where the amplifier is strategically divided into two main sections with the input power evenly split between them. The input signal of the second section passes through a distributed input matching network (DIMN) instead of the gate line of the first section, as in conventional NDPAs. The lower insertion loss of the DIMN at higher frequencies allows for maintaining the driving voltage of the second section at the same level as the first section. This approach effectively addresses the typical gate line attenuation issue in standard NDPAs that often leads to a decrease in power-added efficiency (PAE) as frequency increases. The proposed structure allows for a distinct tapering method for cell sizing, which can further enhance the NDPA performance. Furthermore, the position of the RF choke has been optimized to mitigate the impact of the output parasitic capacitance from the first cell, thereby enhancing the overall performance of the NDPA at the upper end of the operation band. For verification, a distributed amplifier (DA) was designed and fabricated using a commercial 0.12-<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu $ </tex-math></inline-formula>m gallium nitride (GaN) monolithic microwave integrated circuit (MMIC) process. The amplifier exhibits over 10 dB of small signal gain, 3–4 W of saturated output power, and 28%–45% PAE from 3.5 to 15 GHz. Notably, this amplifier demonstrates a relatively consistent PAE in the upper band of its frequency range.