Identification of simple geometrical objects from their backscattered pattern

Both theoretical and experimental work were done in the areas of scattering of incident wave and the generating of creeping waves on simple geometrical objects. Acoustic plane waves of continuous or short pulse form were used in the experimental work where city water was used as the propagation medium. The targets were cylinders, spheres, and cones made out of aluminum, stainless steel, and maple wood, and their dimensions ranged from 10 to 60 wavelengths, which was selected to be 1.5 millimeters. The transducers used as transmitter and receiver were resonant at a frequency of 1 megacycle but these were excited at frequencies lying between 850 to 1050 kilocycles. In the first part of the experimental work, the targets were suspended in water by a thin piano wire support, whereas in the second part these were either completely or partially buried in glazing putty. The backscattered fields for both the continuous and the pulsed wave transmission cases were recorded. The results were compared with the theoretical predictions, and in the cases of spheres and the cylinders, the comparisons were quite satisfactory, while in others the complexity of the target and its orientation imposed some difficulties. In an effort to identify an object by its backscattered field pattern, it was necessary to write two computer programs which would scan and analyze the experimental data. The first program compares the polar data of the bistatic case and the second one analyzes the return of the monostatic pulsed case. Each program identifies a simple geometrical object in the form of the probability of its identification being the same as that for which the reference data was taken. All the experimental data is also presentedin the forms of diagrams and actual photographs of the oscilloscope traces with an adequate explanatory discussion. Finally a method of simulating creeping waves, in weightless environment is suggested (for future satellite laboratories) and compared with Bogush's method.