The fractal quantity was extracted from the frequency characteristics of the scattering matrix S-11 of an extremely weak, 50-GHz backscattered wave; with this quantity, the location of the reflecting body was estimated. In regard to a thin brass wire and a Styrofoam rectangular cylinder, S-11 was measured in the range of 50 +/- 10 GHz. By analyzing the results, the three fractal quantities, that is, dimension, degree of fractal nature, and standard deviation, were extracted. By investigating the behaviors of their variations, it was found that the object location can be estimated even from an extremely weak, scattered wave buried in the measurement system noise. It was shown experimentally that there is an optimal value minimizing the location estimation error in the width of the time window needed for fractal analysis. The value is about 0.7 ns in the case where one brass wire of a diameter of 1 mm is detected. The error of assuming the average location given by the three characteristic quantities as the true location is about 1.5 cm. Also, the response resolution distinguishing the two brass wires with the identical diameter of 1 mm oriented along the wave-radiating direction is about 5 cm. (C) 1997 Scripta Technica, Inc.
