High-Selectivity Circularly Polarized Frequency Selective Surface with Ultralow Profile and Continuous Phase Modulation

In this paper, an ultrathin circularly polarized (CP) high-selectivity frequency selective surface (FSS) with continuous phase modulation is proposed. Based on an antenna-filter-antenna (A-F -A) structure, two circular patches etched with rectangular slots and a stripline filter are cascaded to achieve high roll-off and high selectivity characteristics of FSS. On the other hand, conventional high-selectivity FSS rarely focuses on phase modulation. Continuous and precise phase modulation can be implemented by rotating the A patch in this design. An FSS element operating in the C-band is analyzed and simulated. The results show that this CP FSS, with a thickness of only 0.077 $\lambda$, implements a high-selectivity bandpass response along with good phase modulation. The proposed design can be applied to communication systems to improve electromagnetic compatibility, effectively control interference, and optimize signal transmission.