An Ultra-Wideband Linear-to-Circular Polarizer Based on Phase Difference Complementary Scheme

A novel linear-to-circular polarizer with a bandwidth of 88% is proposed in this paper. It is the first attempt to propose a phase difference compensation method for circularly polarized (CP) bandwidth improvement. Based on this, a new integrated structure combining FSS and dielectric grating structures, named frequency selective surface (FSS) inserted dielectric polarizer (FIDP), is proposed. By combining the monotonically increasing phase difference of the dielectric grating structures, with the monotonically decreasing phase difference of the FSS, the proposed polarizer achieves a 90° phase difference between two orthogonal E-field components within a wide frequency range. At the same time, the magnitudes of the components are not reduced, when the two E-field components pass through the polarizer. Hence, CP conversion over a wide frequency range is achieved. For validation, three feeding horns operating in adjacent bands are designed as the feeds for the polarizer. Experimental results show that the proposed polarizer yields an operating bandwidth of 88%, ranging from 6.8 to 17.5 GHz. The thickness of the polarizer is 1.34 λ0. The performance demonstrates that the proposed structure is a good candidate for X-band applications that require wideband CP wave radiation. It is fabricated by 3-D printing technology and PCB processes, which are low-cost and mature.