2001-Jun-07
Initial results are presented for a 200-300 GHz SIS mixer/preamplifier with an IF bandwidth of 8 GHz. The mixer uses Nb/Al-oxide/Nb tunnel junctions in a circuit with low IF capacitance and inductance. The mixer block mounts directly on the body of a three-stage 4-12 GHz preamplifier which uses discrete InP HFET devices. Mixer bias is provided through the input circuit of the preamplifier. At a LO frequency of 230 GHz, the measured mixer-preamp gain is 30-35 dB, and the DSB receiver noise temperature is 45-57 K across the whole IF band. The preamp alone has 40 dB of gain, and dissipates 7.7 mW. With four amplifiers required in each ALMA cartridge, there is concern that the cooling capacity currently planned for ALMA receivers will be marginal. This mixer/preamplifier has demonstrated that an IF bandwidth of 8 GHz is indeed achievable for ALMA Band 6.
View a pdf version of ALMA Memo 378.
Last modified: June 07, 2001
alma-memos@nrao.edu