230–305 GHz, > 10-dBm-Output-Power Wideband Power Amplifier Using Low-Q Neutralization Technique in 60-nm InP-HEMT Technology

This paper presents a wideband 300-GHz power amplifier (PA) using a neutralization technique. The PA is composed of unit amplifiers (UAs), each of which consists of six-stage common-source amplification stages with a low-Q neutralization circuit. The neutralization circuit includes a transmission-line-based inductor, DC-cut capacitor, and series resistor to broaden the resonance of neutralization. This results in flat input/output impedances and gain characteristics of the amplification stages; therefore, the wideband UA characteristics can be observed. The wideband UA circuit is implemented using this wideband UAs and packaged in a waveguide (WG) module using the ridge coupler as a broadband IC-to-WG transition. The PA has a maximum small-signal gain of 31 dB for 245-250 GHz and saturated output power (Psat) of 11.7 dBm at 265 GHz. Thanks to the low-Q neutralization, the PA module exhibits broadband output-power characteristics, and the Psat is more than 10 dBm for 75-GHz bandwidth, i.e., from 230 to 305 GHz.