A Hybrid Correlation-Dicke Radiometer for Internal Body Thermometry

In this paper, we present a compact calibrated radiometer for measuring internal body temperature. The radiometer architecture combines the benefits of a correlation and a Dicke radiometer. The sensitivity to load impedance variations is reduced through a balanced topology, while the pre-detection switch reduces sensitivity to gain fluctuations of all components in the receive chain that follows. The radiometer is designed to operate in the 1.4-1.427 GHz quiet band using off-the-shelf components on a 10cm×7.6cm printed circuit board. Two types of temperature estimation methods are compared and the errors analyzed using resistors at known controllable temperatures at both input ports. One of the ports is then connected to a near-field antenna probe matched to tissue layers of the cheek. When water of variable temperature is in the mouth, an independent thermocouple verifies the radiometric temperature of the water measured by the probe placed on the skin.