ALMA Memo #284

Optics for the 600-720 GHz Mixer Test Receiver

The Central Development Laboratory is in the process of designing a 600-720 GHz test receiver for evaluating SIS mixers. This test receiver will have provision for a Martin-Puplett Interferometer (MPI) for LO injection/sideband separation, external to the dewar. As the feed horn will be an integral part of the mixer block at this frequency, the optics for the mixer test receiver are designed to be compatible with the ALMA telescopes and as a possible prototype for the ALMA receivers. Two approaches are considered: refractive optics (using lenses) and reflective optics (using mirrors). Two scenarios for the ALMA receivers are presented: (i) where a MPI is used and (ii) where MPI is not needed. The optics were designed using Gaussian beam mode analysis and then checked by more rigorous analysis. Calculated field patterns are shown. The dimensions of the optics for this band have also been determined.

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Last modified: January 28, 2000