A design method of broadband polarizers using metal posts

A broadband cylindrical polarizer with metal posts is designed using the fact that the normalized capacitive susceptances of short posts decreases at high frequencies. The optimum post diameter is measured, and its length which gives negative susceptance and the magnitude of the post susceptance for the two orthogonal polarized waves are determined. The post geometry which gives a broadband differential phase shift is found based on a method utilizing equivalent circuits. Good VSWR characteristics are obtained by having the post susceptance in the matching sections follow the raised cosine distribution. An experimental polarizer constructed using this method has an ellipticity less than 0.25 dB and VSWR less than 1.03 in the percentage bandwidth 12.6%.