Single sideband fixed-tuned design, 8 GHz intermediate frequency band per polarization and state-of-art noise performance are the specifications for the SIS mixers to be used for receiver of Atacama Large Millimeter Array (ALMA). A quadrature sideband-separating scheme that uses two identical SIS mixers with the input signal divided equally between the mixers pumped by a local oscillator with 90 degree phase difference, is a good candidate to fulfill these requirements. This side-band separating mixer technology has been successfully demonstrated for mm-wave band. We introduce a new sideband separation mixer aimed for the ALMA instrument, band 7 (275 - 370 GHz). In the design we use a novel fixed-tuned waveguide-to-microstrip double-probe coupler structure that provides a broadband low-loss distribution of the input RF signal between the two quadrature SIS mixers. We present results of HFSS simulations and scale model measurements at 10 and 100 GHz for this key component of the new receiver, the double-probe coupler. The SIS mixers can be placed on the same substrate with their respective integrated tuning circuitry directly coupled to the waveguide via the probes.

Date Published: 3 July 2000
PDF: 7 pages
Proc. SPIE 4015, Radio Telescopes, (3 July 2000); doi: 10.1117/12.390452

Published in SPIE Proceedings Vol. 4015:
Radio Telescopes
Harvey R. Butcher, Editor(s)