Design of a Miniaturized and Polarization-Independent Frequency-Selective Surface for Targeted EMI Shielding  
[PERSON]  
1 State Key Laboratory of Radio Frequency Heterogeneous Integration, Sino-British Antennas and Propagation Joint Laboratory of MOST, Guangdong Engineering Research Center of Base Station Antennas and Propagation, Shenzhen Key Laboratory of Antennas and Propagation, College of Electronics and Information Engineering, Shenzhen University, Shenzhen 518060, China; [EMAIL_ADDRESS] (Y.H. ); [EMAIL_ADDRESS] (Y.W.j. [EMAIL_ADDRESS] (A.M.) 12222-2223-22  
The FSSs selectively allow certain frequencies to pass through while rejecting or reflecting others, based on their geometrical parameters. Owing to FSSs' filtering capability, they are used in radome design [3], EM absorbers [4; 5], reflectors [6], antenna design [7; 8], radar systems [9], WPT systems [10], polarization rotating surfaces [11], satellite communication [12], electromagnetic shielding [13; 14; 15; 16; 17], and many more. Several configurations of FSSs have been documented in the literature for mitigating electromagnetic interference across various communication bands including GSM, WLAN, WiMAX, C-, X-, Ku-, and millimeter-wave bands. In [18], a single-layer, optically transparent FSS based on a fractal cross-dipole provides dual-band GSM shielding. A low-profile, single-layer FSS utilizing an interdigitated loop element, as described in [19], suppresses radiation emitted from wireless local area network (WLAN) hotspots. This FSS cell resonates at 2.4 GHz and effectively shields across the 1.77 to 3.04 GHz range. It demonstrates wide angular stability and polarization insensitivity; however, its suppression bandwidth decreases with increases in incidence angle for the transverse magnetic polarization mode. The 6 mm \(\times\) 6 mm modified swastika FSS described in [20] stops 5 GHz WLAN signals. The miniaturized symmetric cell structure maintains a stable response for two polarization modes of the incident EM waves up to an angle of 60\({}^{\circ}\). However, the authors did not report measured results for the TM wave mode. Moreover, in [13], a compact convoluted circular loop FSS shield is developed for EMI alleviation. This EM shield selectively filters out signals within a specific frequency range in the X-band, minimizing the impact of external interference on coexisting electronic devices, and revealing wide-angle stability and polarization-insensitivity. An octagonal loop incorporating inductive stubs and patches in [21] achieves wideband rejection characteristics. This flexible FSS effectively rejects the X-band signals with an attenuation of 30 dB at the resonant frequency. It shows good angularly stable shielding performance for both polarization modes, but in the case of TM mode, the rejection bandwidth shrinks as the incident angle increases. A single-layer, dual-polarized FSS based on identical coupled resonators is studied in [22]. It obtains an ultra-wideband response and simultaneously mitigates interference occurring at the X- and Ku-bands. The FSS reveals a polarization-insensitive and angularly stable response with a suppression bandwidth of 63.5% at normal incidence for the TE and TM wave modes. In addition, a multifunctional FSS in [23] enables dual-band transmission in the K-/Ka bands while simultaneously reflecting the X-band signals. It provides an angle-stable response, making it suitable for satellite communications and defense systems. A single-layered FSS comprising vertical and horizontal dipoles with folded arms is analyzed in [24] to shield satellite downlink frequencies. The FSS has a highly stable, polarization-insensitive frequency response up to 85\({}^{\circ}\), making it well suited for selective EMI reduction in satellite communications. In [25], an FSS-based electromagnetic shield, insensitive to the polarization of incident waves, is proposed.