Passive Wireless Programmable FSS for Adaptive Electromagnetic Shielding of Implanted Medical Devices

Implantable Medical Devices (IMDs) such as pacemakers and defibrillators increasingly rely on wireless connectivity for remote monitoring and programming. However, this wireless access introduces significant cybersecurity and physical vulnerabilities, making IMDs susceptible to unauthorized access and electromagnetic interference (EMI). This paper proposes a wirelessly programmable smart shield based on a reconfigurable Frequency Selective Surface (P-FSS) as a novel defense mechanism for IMD security. The shield dynamically transitions between shielding and transparency states, passively controlled by an RFID-powered circuit, ensuring protection from malicious attacks while enabling authorized medical communication. This study extends prior theoretical investigations by introducing a fully functional prototype, realized with a rigorous design methodology and leveraging low-power varactor-based switching to enhance efficiency and miniaturize the size. The system demonstrates over 40 dB of shielding effectiveness in the Medical Implant Communication Service (MICS) band (401–406 MHz) while allowing controlled transparency via a battery-less RFID interface with an activation distance of 0.6 m. Experimental validation confirms the practical feasibility of the proposed approach, making it a viable solution for enhancing the cyber-physical security of IMDs.