Research On Phase Conrol Technology Of Phased Array Focused Ultrasound Based On FPGA

Phased array technology originated from phased array radar.With the development of computer,electronics,materials and other technical fields,phased array technology is developing rapidly in non-destructive testing and medical fields.The phased array high-intensity focused ultrasound technology,as an effective method for the treatment of tumors,has attracted people's attention due to its non-invasive,non-invasive,and sound beam control characteristics.The ultrasonic phased array technology obtains flexible and controllable composite beams and realizes various phase control effects such as dynamic focusing,deflection,and sound beam formation by controlling the phase delay of each element in the ultrasonic array transducer.This paper designs a 64-channel ultrasonic phased array system based on FPGA,completes the key parameter analysis of the ultrasonic phased array,the design of the transmission drive system and the echo acquisition system,and uses the time reversal method to calibrate the focus.The main research contents of this paper are as follows:(1)Research on core parameters of ultrasonic phased array system.According to the principle of phased array transceiver,the calculation method of delay time and the influence of delay resolution on the performance of phased array system are studied.(2)The hardware scheme and system parameter design of ultrasonic phased array system.The overall hardware design scheme of the 64-channel ultrasonic phased array control system is proposed,the functional requirements and parameter indexes of the system are determined,and the corresponding communication protocol is formulated.At the same time,the phased array system launch drive system and echo acquisition system hardware design schemes were formulated.(3)The design of the software scheme of the ultrasonic phased array system.Various delay schemes are compared,the most suitable delay scheme is determined,and the software design scheme of the ultrasonic phased array system is proposed.According to the requirements,the design of the upper computer control interface based on MATLAB and the design of FPGA logic function module with 1ns delay resolution are completed.The interpolation delay estimation method is used to estimate the relative delay difference of the echo signal,so that the echo delay estimation resolution is consistent with the delay resolution of the transmission drive system,and the relative error is reduced.The time reversal method is used to calibrate the focus shift caused by the multi-layered organization,which proves the phase modulation and driving ability of the system.(4)Experimental research.An experimental platform was built,based on the various modules of the test system,combined with the entire ultrasonic phased array system to explore the influence of multi-layered tissue on the focus position,and the focus was calibrated through the time reversal method.The test results show that the delay resolution of the FPGA board-level output pulse signal is within 2ns,and the delay resolution of the sinusoidal excitation signal output by the complete machine after phase calibration is also within 2ns.The maximum deviation of the geometric focus position of the acoustic axis after passing through the multi-layered tissue is2.4mm,and the maximum deviation between the actual deflection distance and the theoretical deflection distance is 1.6mm.The maximum deviation of the geometric focus position after calibration by the time reversal method is0.9mm,and the maximum deviation of the deflection distance is 0.3mm.This proves that the system has good driving and phase modulation capabilities,and this method can better reduce the focus shift caused by the multilayer structure.