Non-Invasive Internal Body Thermometry with On-Chip GaAs Dicke Radiometer

In this paper, we present an on-chip radiometer for non-invasive internal body temperature measurements. The switch and low-noise, high-gain amplifier parts of the Dicke radiometer are designed as a single MMIC using enhancement-mode 0.1μm GaAs pseudomorphic high electron mobility transistor (pHEMT) technology. The radiometer shows 45dB of gain and 0.88dB noise figure at 1.4GHz. When connected to a near-field antenna probe, measurements are obtained on a skin-muscle phantom to track the muscle temperature. The near-field antenna is designed to receive black-body radiation from the 15mm thick muscle phantom under the 2mm thick skin phantom. To retrieve the sub-cutaneous temperature of the muscle, a radiometer calibration is performed with a reference noise source by switching at 10Hz. The integration time of the measurements is 2s. A 30-MHz bandwidth results in an average measurement error of 0.77K compared to a thermocouple measurement of the muscle phantom performed 30s before the radiometric measurement.