Microwave-Acoustic Measurement System for Remote Temperature Profiling in Closed Environments

This paper presents a sounding-system consisting of a doppler radar at 10.0 GHz and an acoustic transmitter, which uses a travelling pulse of ultrasound (about 22 kHz) as an artificial reflector. A new improved measurement system is now reported, which decreases considerably the transmitted microwave power and increases the signal to noise ratio and therefore the maximum range. For the first time, such a system is operated in a closed environment which suffers from high clutter. Air temperature is determined with spatial resolution from the instantaneous speed of the ultrasound pulse. A complete temperature profile over a distance can be obtained in only a few minutes. The effect of humidity on the speed of ultrasound propagation and on the measured temperature profile is clearly demonstrated. The measurement of the relative humidity at a certain position in a closed room with an accuracy of better than 3% RH is also possible. Good agreement with independent measurements is demonstrated.