Abstract
A compact millimeter-wave polarizer that transforms a linear polarization wave into circular polarization is proposed in this paper. The presented polarizer is made of a single-layer metal plate with three ring slots, and the simulated annealing algorithm (SA) is used to optimize the size of the ring slots, which is much more efficient than the manual optimization using commercial EM tools. The optimized resonant frequency of the proposed polarizer is 30GHz, with a 3dB axial ratio (AR) bandwidth of 10%, and a minimum AR value of 0.3 dB at 30GHz.