Modeling and design of antennas for implantable telemetry applications

Incorporating an RF communications link in an implanted medical device can increase its range of applicability and improve quality of life for the patient. Developments in support electronics decrease design risk, but the implanted antenna remains a critical component of a communications link that operates at very low received power. Transmitted power is limited both by regulatory restrictions and, for most implanted devices, by power source capacity. Dielectric losses and wave trapping in the body result in transmission losses much greater than seen in free space communications. Small antenna size is required for physiological acceptability. Design optimization must trade antenna size, geometric complexity and material cost against efficiency, operating bandwidth and driving power. Designs must also work in differing body morphologies. This paper describes the methodology for simulation and the impact of different body morphologies on implant antenna performance. An understanding of these is required to optimize antenna performance and meet ever increasing range requirements. It is shown that depending on the use case and end user morphology, the antenna performance can be incredible successful or marginally adequate. Given the high sensitivity to small changes in thickness of the human body, testing the antenna for a range of BMI and body fat percentages is a must to truly characterize its performance.