High-Resolution Measurements of the Specific Absorption Rate Produced by Small Antennas in Lossy Med - Instrumentation and Measurement, IEEE Transactions on

We describe a thermistor-based technique for measurement of the specific absorption rate (SAR) of radio frequency energy from a small antenna in lossy matter with high spatial resolution. The apparatus employs a small thermistor probe, that is moved about the antenna using a computer-controlled positioning system. The antenna is excited by pulses of radio frequency energy, and the SAR is obtained from the measured rate of temperature increase. We present a simplified thermal model to account for beating of the thermistor by the applied electromagnetic energy, which is a major potential artifact in the method. The apparatus is useful for studies of radio frequency ablation of tissue or near-field exposures in models of the body by wireless transmitters.