SRAM: A Septum-type polarizer design method based on superposed even- and odd-mode excitation analysis

Abstract

This paper proposes an analytical method to design septum-type polarizers by assuming a polarizer as a series of four septum elements with a short ridge-waveguide approximation. We determine parameters of respective elements in such a manner that, at the center frequency, the reflection coefficient of the first element is equal to that of the second one, the reflection of the third one equals to that of the forth, and the electrical lengths of the first, second and third elements are 90 deg. We name this method the Short Ridge-waveguide Approximation Method (SRAM). We fabricated an X-band polarizer, which achieves a cross polarization discrimination (XPD) value of 40.7−64.1 dB over 8.0−8.4 GHz, without any numerical optimization.