A Polarization Insensitive Frequency Selective Surface for Triband GSM Shielding Applications

This article reports on a compact, single layer Frequency Selective Surface (FSS) for tri-band GSM shielding applications. The proposed FSS unit cell comprises of three independent elements. The outermost square ring suppresses GSM-900 MHz signals, the innermost annular ring is incorporated in the design to stop GSM-2100 MHz signals and the middle square ring is used to suppress GSM-1800 MHz signals with a −10 dB rejection bandwidth of 600 MHz, 100 MHz, and 250 MHz, respectively. Furthermore, the proposed FSS exhibits a stable frequency response when illuminated by waves at oblique angles of incidence and a polarization insensitive behavior up-to 60°. The proposed FSS unit cell is realized on an FR4 substrate. A finite prototype containing $8 \times 7$ unit cells with an overall size of $270 \times 230\ \text{mm}^{2}$ is also fabricated and tested. A good agreement between the measured and simulated results showed that the proposed FSS can be employed for suppressing unwanted signals in the GSM-900, GSM-1800 and GSM-2100 bands.