A Compact and High-Efficiency 220-GHz Power Amplifier Module Based on TE $_{11}$ -Mode Radial Power Combiner

A compact and high-efficiency radial power combination amplifier module operating above 200 GHz is presented in this article. This module integrates TE $_{{10}}$ –TE $_{11}^{\rm CP}$ (circularly polarized TE $_{{11}}$ ) mode converters, eight-way TE $_{{11}}$ -mode radial dividers/combiners, rectangular waveguide (RWG)-to-microstrip (MS) transitions, and eight power amplifier (PA) terahertz monolithic integrated circuits (TMICs). Specifically, a high-performance septum polarizer is unprecedentedly employed as the mode converter for the radial divider. By adopting the gap waveguide technology, strict contact between the adjacent waveguide blocks is not necessary, and a high-efficiency power combination is achieved at such high frequencies. The measured return loss of the passive radial divider/combiner is greater than 14 dB, and the average insertion loss is lower than 0.5 dB in the 200–260 GHz range (26.1%-bandwidth), indicating a combining efficiency of 89.1%. Thereafter, a vertical RWG-to-MS transition with a slotted ring resonator (SRR) is presented to achieve a low-loss TMIC package. Last, the active power combination amplifier module produces a maximum output power of 240 mW at 218 GHz with an average combining efficiency of 80.5% within the band of 200–221 GHz.