Compact Flexible Antenna for Brain Temperature Measurement with Microwave Radiometry

We propose a flexible antenna based on a circular complementary split ring resonator (CCSRR) and operating in the narrow 1.4 GHz “quiet” band (reserved for radio astronomy observations). The antenna is designed for microwave noninvasive brain temperature measurements on infants’ heads during therapeutic hypothermia treatment. It is realized on a flexible Kapton substrate and is protected from the skin by a polydimethylsiloxane (PDMS) superstrate. The antenna operates in direct contact with the scalp to collect thermal noise power from the underlying tissue layers and to deliver it to a sensitive radiometer. The CCSRR antenna is investigated with a realistic 4-layer head-tissue model in a planar and 3 different bending scenarios conforming to the curvature radius $(\sim 55 \mathrm{~mm})$ of an infant’s head. Simulation results confirm excellent impedance match and near-field directivity at the desired center frequency of 1.413 GHz and within a narrow bandwidth of ~150 MHz regardless of the bending conditions.