Closed-Form Approximations for RF Radiation from Implantable Medical Devices

The radio frequency (RF) performance of implantable antennas is significantly affected by the lossy biological tissues surrounding the implant. This paper introduces an an-alytical method for assessing the gain and radiation patterns of implantable antennas using planar body models, which are particularly suitable for large host bodies like the human body. The closed-form expressions derived in this method reveal that the antenna gain primarily depends on a few key parameters such as host body complex permittivity, implantation depth, operating frequency, and encapsulation dimensions. A numerical case study featuring an ingestible smart capsule within an anatomical human body model demonstrates the practical application of this method, offering a streamlined approach for assessing RF performance in the early stages of implantable antenna design.