Circularly Polarized Coaxial Horn Filtenna for Electromagnetic Interference Mitigation

This article describes the design of a circularly polarized filtenna based on the insertion of radial stubs into a coaxial horn antenna. These stubs can be placed into the horn body or in the coaxial core, both cases are analyzed in this article. The radial stubs create transmission zeros (TZs) at their resonant frequency producing a stopband filter and preserving the polarization. This solution allows to integrate a filter function into the horn flare, so there is no need for additional space for the placement of an external filter. The gain of the filtenna in the passband is comparable with the gain of a standard horn with the same dimensions. For the chosen use case, the filtenna enables transmission to the ground of scientific data in the passband frequency range and minimizes interference with measurement equipment working in the stopband frequency range. A prototype has been manufactured and its measurements are in accordance with the simulations, validating the design principle.