Radar-acoustic sounding systems (RASS) generally employ a bistatic scheme with the radar source and receiver placed symmetrically beside the acoustic radiator. This paper presents a novel method for combining the acoustic and the electromagnetic waves which reduces complexity, size, and cost of the system and enhances portability. Other advantages of the new monostatic approach are that only one hf-antenna is needed and that no dead zone exists in front of the system. Three possible solutions for realizing a monostatic system are taken into account. The first approach uses a dielectric plate to redirect the acoustic wave. By the second solution the electromagnetic wave is directed into the ultrasonic propagation by a wire grid. Another possibility is to use a composite antenna array made up of acoustic and electromagnetic sources. As no frequency limits exist for the monostatic RASS, it is possible to employ the usual RASS frequencies at 915 MHz or 1290 MHz for the electromagnetic wave. Measurements show that a maximum distance of 30 m can be reached with an uncertainness of +-5 mm at 10 GHz for ranging measurements and +-0.5 K for temperature profiling.
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