Planar inverted-F antenna design for a fully implantable mechanical circulatory support system

Transcutaneous Energy Transfer (TET) is a promising solution to operate implantable mechanical blood pumps such as Left Ventricular Assist Devices (LVAD) without the need for a percutaneous driveline. In order to control the power flow of the wireless energy transfer system and in order to transmit sensor data, a wireless communication channel is needed. This paper describes the design of an implantable Planar Inverted-F Antenna (PIFA) for the use with a TET system, which operates in the MedRadio band at 403.5 MHz and which is suitable for implantation depths of more than 20 mm. The focus of this work is on the practical implementation of the antenna, and the critical design parameters as well as the influence of the human tissue on the antenna design are discussed in detail. Finally, the antenna is built in hardware and the electrical characteristics of the antenna are measured using a muscle tissue mimicking liquid solution. The implemented antenna achieves nearly perfect impedance matching at 403.5 MHz with a return loss of more than 25 dB and a high gain of -26.3 dBi, even for a placement as deep as 20 mm within the tissue mimicking liquid. Numerical simulations further show that a maximum spatial-average SAR of 0.27 W/kg is achieved in the muscle model with the maximum allowed antenna input power of 9.35 dBm, which is a factor of six below the most stringent SAR limit of 1.6 W/kg.