Broadband H-Band Power Amplifier with Optimum Intermediate Splitter and Combiner Impedance

This paper reports the successful application of an optimum intermediate impedance in the splitter/combiner structure between the parallelization paths of a five-stage common-source amplifier design to achieve a broadband power amplifier. The amplifier has a record S21 bandwidth of 84 GHz between 226 and 310 GHz. This conventional common-source design is competitive regarding bandwidth with inherent broadband H-band traveling-wave amplifiers but offers a larger maximum gain of 19.9 dB. An OP(1dB) of more than 8.2 dBm is measured at 243 GHz, while exceeding existing common-source designs by 27 GHz in small-signal bandwidth.