A 32-Gigahertz Coupled-Cavity Maser Design

A 32-GHz coupled-cavity maser design is described. The theory and the predicted performance of cavity masers are included. A coupling cavity in the signal waveguide enables tuning of the maser over the 500-MHz-wide deep-space frequency allocation from 31.8 GHz to 32.3 GHz. The ruby cavity is simultaneously resonant at 32 GHz in the TE101 mode and at the pump frequency of 66.4 GHz in the TE301 mode. A pump rejection filter is incorporated to help confine the pump energy to the ruby and coupling cavities. A mode-matching analysis program was used to determine the dimensions and the tolerances for this design. Equivalent circuits using lumped elements showing characteristics of the cavities, filters, and ruby spin system were generated. A 3.1-K maser noise temperature in a 2.2-K cryogenic refrigerator is predicted at 32 GHz.