A Miniaturized Four-Element MIMO Antenna With EBG for Implantable Medical Devices

A miniaturized four-element multiple-input-multiple-output (MIMO) antenna operating in the band of Industrial, Scientific, and Medical (ISM) 2.4-2.48 GHz is investigated to supply sufficient transmission rate and fight against multipath fading. A single antenna integrates with dual radiators, and each radiator is owned by a pair of subantenna units, greatly diminishing the whole dimensions of the implanted MIMO device. A cross-shaped slot etched in the radiator, a branch extending on the conductor ground, and a pair of electromagnetic band gaps are integrated to achieve high isolation. The proposed MIMO antenna has the compact dimensions of 18.5 mm x 18.5 mm x 1.27 mm. The simulation in the three-layer phantom indicates that the impedance matching is good with a bandwidth of 18.64% (2.14-2.58 GHz) and a maximum gain of -15.18 dBi and the mutual coupling is reduced to less than -15.99 dB at the ISM band. An ex-vivo test was implemented in a fresh pork slab, and the measurement results are well matched with the simulation ones. Health safety considerations and link budget are discussed to validate the antenna's availability in biomedical telemetry, and the envelope correlation coefficient is computed, illustrating the high independence between antenna elements.