A 200-300 GHz SIS mixer-preamplifier with 8 GHz IF bandwidth

A 200-300 GHz SIS mixer-preamplifier with an IF bandwidth of 8 GHz Is described. The mixer uses Nb/Al-oxide/Nb tunnel junctions in a circuit with low IF capacitance and inductance. The mixer block is designed to mount directly on the body of the 4-12 GHz InP HFET preamplifier and mixer bias is provided through the input circuit of the preamplifier. At a LO frequency of 230 GHz, the mixer-preamp gain is 30-35 dB, and the DSB receiver noise temperature is 45-57 K across the whole IF band. This is the largest instantaneous bandwidth reported to date for an SIS receiver.