Conformal multi-channel MIMO antenna for implantable leadless transcatheter pacing systems

Abstract

This article presents a conformal multi-channel multiple-input-multiple-output (MIMO) antenna designed for a leadless transcatheter pacing system (TPS), operating across the medical implants communications services (MICS) band (401–406 MHz), the wireless medical telemetry services (WMTS) bands (0.608 GHz and 1.4 GHz), and the industrial, scientific and medical (ISM) bands (0.433 GHz, 0.915 GHz, and 2.45 GHz). The proposed antenna has a size of 19 mm × 10 mm × 0.068 mm (0.047λg × 0.025λg × 0.0001λg), and it is constructed on a thin polyimide substrate and wrapped around the TPS capsule’s inner wall, efficiently utilizing the inner space. For the simulation, the proposed antenna and TPS capsule containing dummy electronics are positioned within a homogeneous three-layered phantom (skin-fat-heart) with dielectric properties that mimic the human heart, as well as in a realistic heterogeneous voxel model (Gustav). The antenna is validated for a real environment using an ex-vivo setup comprised of fabricating the antenna prototype and measuring its performance metrics inside pork meat and phantom solution. The proposed MIMO antenna offers good isolation (>25 dB) between antenna elements, and the impedance bandwidths are 710 MHz (0.34 to 1.05 GHz), 560 MHz (1.26 to 1.82 GHz), and 990 MHz (2.01 to 3 GHz). Further, MIMO characteristics are evaluated, and antenna robustness and safety are tested by considering specific absorption rates using human voxel models. The proposed MIMO antenna is the thinnest conformal antenna designed to cover essential biotelemetry frequency bands, including low frequencies of 0.402 GHz and 0.433 GHz with circular polarization, which significantly reduces power consumption and improves transmission range, making it a viable candidate for wireless TPS applications.