Simple 1 mm receivers with fixed tuned double sideband SIS mixer
and wideband InP MMIC amplifier

G. Engargiola, A. Navarrini, R. L. Plambeck
Radio Astronomy Laboratory, University of California, Berkeley

and

N. Wadefalk
Electrical Engineering Department, California Institute of Technology, 

ABSTRACT

We report on attempts to broaden the IF bandwidth of the BIMA 1mm
Superconductor-Insulator-Superconductor (SIS) heterodyne receivers
by combining fixed tuned  Double Side Band (DSB) SIS mixers and
wideband MMIC IF amplifiers.  To obtain the flattest receiver gain
across the IF band we tested three schemes for keeping the  mixer
and amplifier as electrically close as possible. In Receiver I,
we connected separate mixer and MMIC modules by a 1" stainless
steel SMA elbow. In Receiver II, we integrated mixer and MMIC
into a modified BIMA mixer module.  In Receiver III, we devised
a thermally split block where mixer and MMIC can be maintained
at different temperatures in the same module -- in this receiver
the mixer at 4 K sees very little of the 10-20 mW heat load of the
biased MMIC at 10 K. The best average receiver noise we achieved
by combining SIS mixer and MMIC amplifier is 45-50 K DSB for nLO =
215-240 GHz and below 80 K DSB for nLO = 205-270 GHz. Over a 1-4 GHz
IF we have demonstrated receiver DSB noise temperatures of 40-60 K. 
Of the three receiver schemes, we feel Receiver III shows the
most promise for further development.