H-band power amplifier integrated circuits using 250-nm InP HBT technology

In this paper, H-band (220-325 GHz) power amplifier (PA) integrated circuits (ICs) are presented using 250-nm InP HBT technology, where a cascode topology was adopted to achieve high gain and high output power. Three PAs were designed: PA1 was implemented with two-stage cascode HBTs, PA2 combined two PA1s, and PA3 combined four PA1s, by using Wilkinson couplers without isolation resistors. Electromagnetic simulations were carried out for the accurate design of passive circuits such as a microstrip line, a capacitor, and RF pads. The measured insertion loss of the RF pad and Wilkinson coupler was as low as 0.24 dB and 0.70 dB, respectively, at 300 GHz. The three PAs exhibited a measured gain higher than 15 dB with good return losses at 300 GHz. The output powers scaled well with total emitter area of the PAs. PA3 exhibited a maximum output power of 13.5 dBm at 301 GHz. To the best of the authors' knowledge, this corresponds to the highest output power among the previously reported solid-state PAs in this frequency range.