First Analog Linearization of a 300-GHz Power Amplifier: Demonstration and Quantification

This work demonstrates the first analog linearization of a 300-GHz solid-state power amplifier module using a single class-C stage as a predistorter to counteract gain and phase compression of the main amplifier. The circuit is implemented in a 35-nm indium gallium arsenide metamorphic high-electronmobility transistor technology, and the large-signal phase behavior of class-C biased amplifiers is characterized at sub-millimeterwave frequencies for the first time. Operating the predistorter at its optimum bias improves the output-referred 1-dB compression point of the main amplifier by 1.3-3 dB across 280-317.5 GHz and shifts the1∘phase-compression point by 2.9 dB at 295 GHz. Under low-drive conditions, modulated measurements at 295 GHz with 1.35GHz bandwidth show a 0.9% EVM reduction and a 7.2 dB ACPR improvement. These results set new benchmarks for analog predistortion at millimeter-wave and sub-millimeterwave frequencies. Furthermore, methods for quantifying EVM via complex alignment and orthogonal projection, as well as spectral regrowth, are proposed and experimentally validated.