Wide Passband and High-Selectivity Frequency Selective Surfaces Based on Filtering Antennas

The paper presents a frequency selective surface (FSS) design method based on the filtering antenna proposed. Firstly, the design of bandpass FSS based on antenna-antenna architecture and low-temperature co-fired ceramic (LTCC) process. The antenna is selected as a dual-polarized patch antenna with an L-probe feed. Next, a filtering method using a parasitic band-stop structure is used to design the filtering antenna. Finally, two identical filtering antennas sharing a common floor are placed back-to-back and the feed metal posts are connected through holes in the floor. Introducing an equivalent transmission line model for further analysis. The resulting FSS based on a filtering antenna-filtering antenna (FA-FA) has excellent polarization uniformity and angular stability with flat in-band frequency response and fast roll-off. Simulation results show that the proposed FSS has a bandwidth of 24.31 to 30.01 GHz, covering the $5 \mathrm{G} \mathbf{n 2 5 7 / n 2 5 8 / n 2 6 1}$ bands when $\left|\mathrm{S}_{21}\right|$ exceeds 10 dB. Three transmission poles (TPs) effectively broaden the bandwidth. Three transmission zeros (TZs) near the passband provide good out-of-band cutoff. In addition, the proposed FSS is compact and does not require additional filtering circuits, and also has the advantages of adjustable zero and dualpolarization applications.