Experiments on transmitting and receiving an ultrasonic pulse train with stacked piezoceramic transducers

Abstract

In ultrasonic flaw detection and medical diagnosis, shorter pulses tend to be used for improvement of the time resolution. It is then necessary that the transmitting and receiving systems have large bandwidth. In order to obtain information from the ultrasonic wave in the propagation direction over a long distance, a pulse with high peak power needs to be used so that the SIN is enhanced. However, it is not simple to attain the requirements for both large bandwidth and high SIN. In this paper, a system is proposed in which, instead of using short pulses, the transmitted pulses are combined into a pulse train and pulse compression is carried out on the receiving side by a correlation process, so that short pulse transmission is realized effectively. First, we describe the generation of an ultrasonic pulse train using a stacked piezoceramic transducer made of several piezoceramic resonators without complex electronic circuits. We next describe the principle of the reception correlation process, using stacked transducers with the same characteristics. We fabricated stacked transducers for transmission and reception of an ultrasonic pulse train with a Barker code of length 7. Transmission and reception experiments show that both the transmission of the pulse train and the correlation process are possible. Transmission and reception experiments were carried out under different SINconditions by adding external noise to the input. When the SIN ratio of the transmitting pulse train was 0 dB, a gain of 4.6 dB was obtained. The gain margin was found to be 7.2 dB. Hence, it was demonstrated that the present method is effective under low SIN conditions. 0 1997 Scripta Technica, Inc.Electron Comm Jpn Pt 2,79( 12): 1-9, 1996