A 243 GHz low-noise amplifier module for use in next-generation direct detection radiometers

A compact H-band (220-325 GHz) low-noise amplifier circuit has been developed, based on a grounded coplanar waveguide (GCPW) technology utilizing 50 nm metamorphic high electron mobility transistors (mHEMTs). The realized four-stage cascode LNA achieved a small-signal gain of 31 dB at 243 GHz and more than 28 dB in the frequency range from 218 to 280 GHz. Coplanar topology in combination with cascode transistors resulted in a very compact die size of only 0.5 × 1.5 mm
²
. For low-loss packaging of the circuit, a set of waveguide-to-microstrip transitions has been realized on 50 μm thick GaAs substrates demonstrating an insertion loss of less than 0.5 dB at 243 GHz. The realized LNA module achieved a small-signal gain of 30.6 dB and a room temperature (T = 293 K) noise figure of 5.6 dB at the frequency of operation.