Wideband circular polarizer based on dielectric gratings with periodic parallel strips.

A wideband linear-to-circular polarizer is proposed, which consists of an array of dielectric slabs with double-sided parallel metallic strips. The polarization conversion is achieved by decomposing the linearly polarized incident plane wave into two orthogonal components of equal amplitude, which are subjected to an unequal phase shift such that the resultant phase difference between two components is 90° after an appropriate propagation path. The metallic strips are introduced to enhance the axial ratio bandwidth. Microwave experiment is performed to successfully realize these ideas and measured results are in good agreement with numerical simulations. The frequency range over which the measured transmission coefficient is higher than 0.95 is from 7 to 13.7 GHz, and the 3 dB axial ratio bandwidth under normal incidence ranges from 7 to 13 GHz, corresponding to a 60% fractional bandwidth. In addition, the proposed polarizer shows a good stability with respect to the oblique incidence.