LOW-COST REMOTE TEMPERATURE SENSOR FOR MICROWAVE AND RF HEATING USING MICROWAVE RADIOMETRY

While microwave radiometry has been used for remote temperature measurement in microwave and RF heating applications in the past, the complex and expensive instrumentation required has limited its range of applications. Recent advances in low-noise, low-cost microwave amplifiers for consumer products should make it possible to design lower-cost radiometers for a wide range of industrial applications in the future. This paper describes the use of a low-cost microwave satellite receiver in a 12-GHz radiometer system to remotely measure the temperature of wood, rubber, and carbon adsorbent. After calibration, the radiometer's accuracy is typically within +/- 5 degrees C or better over a range of 25-70 degrees C. With high-loss materials such as carbon, the radiometer senses temperature within a few mm of the surface. With lower-loss materials such as rubber and wood, the radiometer detects temperature changes in water-bearing regions as deep as 1 cm below the surface. The experimental data presented compare favorably with theory.