A frequency modulated (FM) FSCW radar technique that uses the envelope delay to determine range information is described. The analysis shows that the measured delay produced by the FM FSCW system consists of a term proportional to the delay of the strongest reflection and a superimposed oscillation with a period equal to the difference in the target delays. A practical system able to measure target distance by determining the delay experienced by a tone modulated FM test signal reflected from the two targets is described, A feature of this design is the use of a digital phase detector based upon an IQ correlation algorithm to accurately measure the modulation phase delay and, hence, distance. While the system is being developed to measure the bagasse-water interface at the diffuser in a sugar milling process, the technique is quite general and could be applied to other close-range radar problems.
['Douglas L. Maskell', 'Graham S. Woods']
A frequency modulated envelope delay FSCW radar for multiple-target applications