A 1–160-GHz InP Distributed Amplifier Using 3-D Interdigital Capacitors

A wideband monolithic microwave/millimeter-wave integrated circuit (MMIC) distributed amplifier (DA) using a 3-D interdigital capacitor at the input of the gain cell is demonstrated in an indium phosphide (InP) heterojunction bipolar transistor (HBT) process. The proposed DA using interdigital capacitors improves the input return loss at high frequencies compared with the one implemented with conventional metal-insulator- metal (MIM) capacitors. The fabricated amplifier achieves a measured average gain of 10.5 dB over a 3-dB bandwidth from 1 to 160 GHz. The maximum measured saturated power (P
_sat
) is 17.8 dBm with the corresponding 1-dB compression power (P
_1dB
) of 15 dBm at 55 GHz. The amplifier achieves a minimum P
_sat
of 14.6 dBm up to 110 GHz.