An Overview of Medical Implant Antennas

Antenna miniaturization for integration with small implants for sensing, wireless powering, and communication is a multi-parameter design task. The implanted antenna performance is governed by the antenna size, operating frequency, antenna surrounding tissues, subsequent biological tissues, antenna encapsulation, the electronics and metal objects nearby the antenna, implant depth, and the electromagnetic radiation source defined by the antenna geometry. The antenna performance can be characterized by impedance matching, bandwidth, antenna near-field, far-field radiation pattern, efficiency and gain, and the specific absorption rate (SAR). This paper reviews the design steps for miniaturized implant antennas, the frequency dependency of biological tissues, and EM modeling and simulation tools to support the design. Examples of miniaturized implant antennas are provided for application in the cardiac, gastric, and brain.