A 275-GHz InP HBT H-Band Amplifier With Transmission Line-Based Capacitively Coupled Resonator Matching Technique

This article presents transmission line-based capacitively coupled resonator matching techniques for THz amplifiers and demonstrates the idea in a three-stage differential H-band amplifier in indium phosphide (InP) 250-nm double heterojunction bipolar transistor technology for a general-purpose waveguide gain block. We propose two types of symmetrical capacitively coupled resonator matching circuits with transmission lines, which are effective for replacing low-quality lumped elements at subterahertz frequencies. For high stability and high gain, the cascode topology was optimized with series and shunt interdevice matching circuits. The amplifiers were fabricated in two versions; one with folded rat-race baluns for on-chip measurement and the other with on-chip dipole couplers for split-block waveguide packaging. From 252 to 295 GHz and 258 to 293 GHz, the measured peak gains were 23 dB in the on-wafer amplifier and 20.8 dB in the packaged amplifier, respectively, achieved with a 3.6-V supply at 46 mA and a 3.0-V supply at 37 mA.