Size Effect Study on High Frequency Transducers for Sensitivity Enhancement

In a high frequency ultrasonic imaging system, high signal-noise-ratio (SNR) is highly demanded to acquire high quality images. Transducer sensitivity enhancement is essential to increase the SNR. In this work, size effect of transducers with working frequency 12MHz and 20MHz is systematically studied to find its relationship with sensitivity. FEM (Finite Element Method) models are built to analyze the impedance and sound field characteristics for different size transducers. Pulse-echo measurement experiments are carried out to compare the performance variation induced by the size effect. Simulation results suggest that working frequency is mainly determined by the piezoelectric slice thickness, the values of admittance are dependent on the area value of transducers and the optimum width is 1.5mm-1.7mm for 12MHz transducer and 1.1mm-1.3mm for 20MHz transducer. The admittance measurement results and pulse-echo results confirm the simulation conclusion and certify that 12MHz transducer with 1.5mm width and 3.0mm length, 20MHz transducer with 1.2mm width and 3.0mm length have the highest sensitivities. Their echo peak-peak values can reach 1.248V and 1.332V, respectively. These results indicate that sensitivity can be enhanced by optimizing transducer size. Methods utilized in this work are of great significance in a broader range of transducer design cases such as IVUS system and array transducers.