Ultrasonic Detection using Wideband Discrete Wavelet Transform

algorithms, the geometrical properties such as size, shape, and orientation, of objects can also be investigated by ultrasonic imaging methods. An inherent problem with ultrasonic detection is the conflict between signal-to-noise ratio and resolution. If good resolution is to be obtained, the transmitted pulse cannot be long in duration. If short ultrasonic pulses are used, their energy is small and hence will result in small signal-to-noise ratio. Pulse compression techniques have been used to overcome this problem. In this paper, the Wavelet Transform and Cross Wavelet Transform are employed to process the ultrasonic signals to obtain a high-resolution image map and then to determine the size and orientation of a straight-line object. Abstract This paper describes the design of a wideband spatial processor for the detection of a straight-line object by an ultrasonic pulse-echo detection system. An ultrasonic pulse is transmitted from the transducer and the two wavelets diffracted form the two end points of the straight-line object are received by three spatially separated receivers. Three stages of signal processing are carried out. At the first stage, the Mother Wavelet operator generates three sets of two-dimensional wavelet coefficients. At the second stage, cross wavelet transforms are performed on wavelet coefficients obtained in the first stage. At the third stage, cross wavelet transforms are performed on cross wavelet coefficients obtained in the second stage. As a result of this three-stage operation, a high-resolution image about the environment is generated and the range and bearing of the two end points of the straight-line object are obtained. A simulation program is developed to investigate the processing algorithm in an ultrasonic detection environment.