Computation of available RF power inside the body and path loss using in vivo experiments

摘要

A radio frequency (RF)-based medical device implanted deep inside a human body can be wirelessly powered using RF energy. However, this method experiences loss in the form of attenuation and absorption, which is caused by the lossy human body. The need for a path loss (PL) model is, therefore, necessary to characterise these losses. This study presents a novel PL method, which is based on the |S21| measurements, obtained from a series of experiments on two different Dorset breed ovine models. Also, the uncertainty analysis of the equipment has been performed and the available RF power inside the body at a proposed implant location has been computed. The results are then used to develop and propose an equivalent model for PL in an anechoic chamber. Overall, an approximate PL of 3.5dB/cm in the ovine body was measured at 1.2GHz. Moreover, it was concluded that with the inevitable errors in the equipment, the total PL for 6cm deep implant location was approximate to 21dB with an uncertainty of 2.034dB. The PL model presented is novel and has a great potential for applications in the design and development of RF-based implantable devices, especially leadless pacemakers.