A balanced 150–240 GHz amplifier MMIC using airbridge transmission lines

A compact balanced amplifier monolithic milli-meter-wave integrated circuit (MMIC) for the frequency range from 150 to 240 GHz is developed using airbridge microstrip (AirMS) transmission lines in a 35nm gate-length metamorphic high electron mobility transistor (mHEMT) technology. The hybrid couplers for the balanced design are realized using airbridge-stacked coupled lines. The balanced three-stage cascode amplifier achieves a small-signal gain of more than 15 dB between 150 and 240 GHz, from 210 to 230 GHz even more than 23 dB. In the latter frequency range the variation of the measured gain curve is less than 0.8 dB. Due to the balanced design, the input and output reflections are lower than −12 dB up to 227 GHz, and lower than −6 dB in the whole frequency range.