Conformal ultra-miniaturized frequency selective surface for medical shielding applications

This article presents a novel wearable frequency selective surface (FSS) for shielding the communication link of implantable devices with the external environment. The proposed shield blocks a dual-band frequency operating at 404 MHz and 2.45 GHz in the medical implant communication service (MICS) and industrial, scientific, and medical (ISM) bands. The two distinct stop bands provide a high-frequency band ratio of 6.02 in an ultra-miniaturized physical form factor of 0.024 lambda o x 0.024 lambda o, with at least 76.96% miniaturization when compared to the existing art. Each of the unit cells is imprinted on a conformal 50 mu m polyester substrate in a symmetrical configuration. The polyester adheres with jean to realize its compatibility with wearable applications. The designed shield system offers a low profile of only 0.00146 lambda o. By suppressing the grating lobe, the proposed shield achieves a high angular stability of 80 degrees and polarization insensitivity of 90 degrees in both transverse electric (TE) and transverse magnetic (TM) modes. The FSS is fabricated and measured results validate its performance. To evaluate the physical insight, an equivalent circuit model (ECM) analysis is done. To ensure durability, the proposed shield system is tested with Amitech SDR04. This work proposes a low-cost conformal ultra-miniaturized frequency selective surface (FSS) for shielding medical application bands such as MICS (404 MHz) and ISM (2.45 GHz) bands with a 10 dB shielding of 55.1 and 26 dB having a bandwidth of 438 and 390 MHz, respectively. The proposed polarization-insensitive FSS unit cell achieves the ultra-miniaturized form factor of 0.024 lambda o with a high angular stability of 80 degrees in both transverse electric (TE) and transverse magnetic (TM) modes. image