Cryogenic millimeter-wave ring filter for space application

A tunerless cryogenic millimeter-wave ring filter has been designed for a space application. Detuning of the center frequency caused by thermal deformations has been compensated by a novel mechanism based on the use of two materials,vith different temperature expansion coefficients. An improvement of 1 : 8 in the detuning of the center frequency, compared to an uncompensated ring filter, is reported. By applying the new design, external tuning aids can be avoided even in applications where a wide operational temperature range is of interest. Thus, the new ring filter is especially advantageous in space-borne millimeter-wave receivers.