A new approach to reduce the helical resonator discharge in RF filters used in spacecrafts

Helical filters are widely used in the UHF/VHF frequency range, for their smaller size and high Q. For ambient operation, the design is simple and can be realized using commercially available components. Whereas at lower pressure levels, mostly, due to degaussing property of the dielectric material there could be a sudden discharge or a breakdown inside the cavity that houses the helix and thereby the normal operation of the filter gets affected. This may lead to raise in noise floor or intermittent power output. In this paper, a new technique for suppressing such a discharge is discussed. This can be applied even to the filters that are already fabricated. Filters designed by this method were tested successfully in thermo-vacuum chambers up to 10^-6 Torr without any problem and results of various tests are presented.