3B-5 Development of an Ultrasonic Array Technique for LSAW Measurement

An ultrasonic method of leaky surface acoustic waves measurement employing focused transducer and linear array mounted in a pitch-catch arrangement is considered. We present the wave theory of the system and demonstrate that the spatio-temporal spectrum of the output data set can be expressed as a product of the reflectance function of the liquid-specimen interface and overall transfer function of the system. By processing data in the spectral domain, it is possible to obtain parameters of dispersive waves. Using the wave model, it was shown that the angular resolution of the system increases with increasing of the number of the elements of the array and depends on the tilt angle of the array. Also, the problem of spatio-temporal spectrum aliasing was considered, and the maximal value of the pitch of the array was estimated at a given tilt angle of the array and directivity of the transmitting and receiving transducers. The results of the theoretical consideration were confirmed by the test experiments carried out in the 20 MHz frequency range