Narrow Bandpass Frequency Selective Surface With High Level of Angular Stability at Ka-Band

In this letter, a novel design of a narrow bandpass frequency selective surface (FSS) based on the utilization of the coupled method, which resonates at Ka-band frequencies between 29 and 30.3 GHz, is proposed and experimentally evaluated. A high selectivity was achieved, by coupling two metallic layers, which were based on the structure of a cross aperture and a rectangle grid patch, respectively. The simple symmetric patterns used in the proposed work have also made the FSS independent of polarization properties. Moreover, a high angular stability was also achieved since for electromagnetic (EM) wave incident at degrees from 0 degrees to 75 degrees, the frequency deviations were only 0.1% and 0.4% for TE and TM polarizations, respectively. For performance evaluation, an experimental FSS prototype was fabricated by a double-sided printed circuit board (PCB), which was composed of 50 x 50 unit cells in a dimension of 18 cm x 18 cm. A Keysight N5227A PNA and two-horn antennas in a chamber were setup to measure the performance. The experimental measurement results have shown a good agreement with the numerical simulations.