220-GHz High-Efficiency InP HBT Power Amplifiers

This paper reports on two power amplifier (PA) monolithic microwave integrated circuits (MMICs) operating at frequencies around 220 GHz. The PAs use 250-nm InP HBTs and thin-film microstrip technology formed with a benzocyclobutene dielectric. Both PAs utilize a two-emitter-finger HBT unit-cell with each finger having an emitter area of 0.25×6 μm². The single-stage amplifier MMIC has six two-emitter HBTs in parallel for a total emitter area of 18 μm². This amplifier has ~ 5 dB of small-signal gain from 210 to 230 GHz. It has demonstrated saturated output power of 90 mW at 210 and power-added efficiency (PAE) of 10%. This is the highest PAE number demonstrated at these frequencies. The two-stage PA uses three single-stage PAs, one as a driver and two in a balanced configuration in the second stage. The total output emitter area is 18 μm². This PA demonstrated saturated output > 100 mW and PAE ≥ 4% from 210 to 225 GHz.