Summary
International Symposium on Antennas and Propagation
2012
Session Number:2E2
Session:
Number:2E2-5
Beam Focused Slot Antenna for Microchip Implants
Yuji Tanabe,
pp.-
Publication Date:2012/10/29
Online ISSN:2188-5079
Summary:
Wireless powering of implantable medical devices such as pacemakers, cardiac defibrillators and other devices for post-surgery monitoring and drug delivery enables device miniaturization and obviates risks associated with lead wires and battery replacement. Traditionally, inductively-coupled coils have been considered the primary candidate for power transfer since they operate at frequencies sufficiently low to ignore losses in tissue. Recently, however, it was shown that the optimal frequency for wireless power transfer to a miniature implant is in the low-GHz range despite increased tissue absorption. At low-GHz frequencies, the power transfer efficiency was significantly improved by considering transmitter structures more complex than the coil. In particular, the optimal transmitter was found to exhibit beam focusing, which invokes constructive and destructive interference to maximize the fields at the receiver while minimizing heating in tissue. The optimal transmitter, however, was derived in terms of a surface current distribution and was not physically realized. This paper proposes a beam focused transmitter implemented by four curved slot antennas and a 4-port feed network that synthesizes the optimal current distribution. We first examine the dominant current for a receiver modeled as a magnetic dipole (i.e. small coil) and obtain a simplified current distribution. The simplified distribution is realized by a pair of slot antennas which is used to design an array that is robust to the horizontal orientation of the receiver coil.