Design, modelling, construction and evaluation of a 64-element, 1 MHz ultrasonic probe

An ultrasonic probe with 64 elements, operating at the centre frequency of 1 MHz has been designed using 1-3 piezocomposite. An electrical equivalent circuit model is developed to predict its ultrasonic characteristics. The probe consists of three functional layers, namely, a piezocomposite active layer, a matching layer and a backing layer. These layers are represented by their individual T-networks and cascaded together to represent the complete probe. Voltage Transfer Function (VTF) is derived to determine the electrical and the ultrasonic characteristics of the probe. The results of transmission line model are verified by Finite Element Model (FEM) studies. Two commercial FEM packages, namely, ATILA and OnScale are employed for the comparative studies. The model results are validated by constructing an ultrasonic probe and evaluating its characteristics. The electrical impedance, Transmitting Voltage Response (TVR), Receiving Sensitivity (RS), Two-way Insertion Loss (IL) are determined by all these methods independently. The TVR, RS, IL and bandwidth of the ultrasonic probe at 1 MHz are found to be about 175 dB, -200 dB, 30 dB and 400 kHz, respectively. The results predicted by three types of modelling studies agree well with each other and with experimental data. The waveform and spectrum predicted by OnScale model agree with the experimental data. The 64-element ultrasonic probe presented in this work is suitable for electronic beam-steering in azimuth and can be used for ultrasonic imaging applications.