Design And Realization Of Ultrasonic Phased Array Focusing System

Acoustoelectric modulation is based on the acoustoelectric effect that the focused ultrasound cause small elastic deformation in local area,leading to changes in conductivity.The effective fast scanning of focused ultrasound on the measured medium is the basis of the acoustoelectric modulation,which is the key to improve the quality of image reconstruction.The focusing precision and focusing parameters directly affect the accuracy of the final reconstructed image.Ultrasonic phased array change sound waves sending from each element to reach a point in the object by controlling the excitation pulse time delay of each element in array transducer,to achieve changes of the focus and beam azimuth,then finally achieve beam synthesis.Ultrasonic phased array use the array structure without the need to move the position of the probe scanning mechanism,so the system is more simplified and reliable,but still have a high resolution and a high S/N ratio.The amplitude of combined waveform with the ultrasonic phased array is a lot higher than single wave,which can improve the ultrasonic focusing characteristics and reduce the difficulty of the extraction of acoustoelectric signals.The topic was mainly based on the background of ultrasound modulated electrical impedance tomography.Based on the analysis of the focusing characteristics of ultrasonic phased array acoustic beam,a hardware platform for ultrasonic phased array focusing system for acoustic-electrical imaging is designed.The main results and conclusions are as following:(1)The analysis of the focusing characteristics of the phased array is made.The geometric characteristics of the focus are analyzed,including the depth of focus and the size of the focal spot.The influence of each parameter is analyzed and optimized to improve the transducer.The feasibility of focus coverage is analyzed.The results show that the focus coverage can optimize the acoustic beam,and eliminate the scanning blind spot.It can improve the accuracy of focusing in biological tissue,and the quality of acoustic-electrical imaging.The simulation results are verified by simulation of sound field model.(2)Based on the research work related to exciting single-channel ultrasonic emission system,a 16-channel ultrasound phased array focusing system,including functional modules,parameter indexes as well as system control structure,was designed.Based on the completed circuit board and the design of the controlling program to debug the entire focus system,the corresponding data is collected.Finally the results of the data are analyzed in detail.