Research On Hardware Implementation Method Of Ultrasonic Signal Sparse Sampling Based On Finite Rate Of Innovation

In ultrasonic testing,in order to improve the detection efficiency,defect detection rate and quantization accuracy,the sensor array structure or the probe with high center frequency is often adopted,which will produce a huge amount of data,bring great difficulties to signal acquisition,transmission and storage.Meanwhile,the hardware requirements are higher,the widespread use of this technology is seriously restricted.Recent years,the research on reducing the sampling rate and the amount of data acquisition has attracted the attention of scholars.With the introduction of FRI(finite rate of innovation)sampling theory,it is possible to reconstruct the original signal accurately from discrete sparse data,obtained by equal interval sampling with a low speed of finite rate of innovation.However,FRI sampling is still in the theoretical research stage.The sparse data is usually obtained by secondary sampling from the discrete data,sampled from the original signal according to the normal Shannon-Nyquist sampling theorem.There is no real hardware implementation of FRI sampling system so far.To this end,based on the analysis of FRI sampling theory,we carry on research of the FRI sampling principle and hardware realization method of ultrasonic signal,and realize the FRI sampling from the perspective of hardware.Firstly,the principle of FRI sampling and the sampling framework of ultrasonic signal are researched in this thesis.Then,focusing on the research of method of ultrasonic pulse stream forming,sampling kernel implementation and finite length signal FRI sampling,ultrasonic pulse stream forming method based on quadrature demodulation technique,sampling kernel implementation method based on analog low-pass filter approximation,and hardware realization method of finite length signal FRI sampling are proposed in this thesis.After that,hardware circuit design,making and debugging are completed.Through the application of the actual circuit in the ultrasonic inspection of pipeline defects,the FRI sparse sampling of ultrasonic signal is realized from the perspective of hardware for the first time.The experimental results show that this technique can greatly reduce the amount of sampling data,and can obtain the ultrasonic echo signal from the sparse sampling data,and then reconstruct the original signal accurately.The main research works of this thesis are as follows:(1)Based on the analysis of the principle and method of ultrasonic signal FRI sampling,ultrasonic pulse stream forming methods are analyzed theoretically.A method of ultrasonic pulse stream forming based on quadrature demodulation technique is proposed.The condition that the frequency,bandwidth,carrier frequency and low-pass filter band should be satisfied in the hardware implementation are studied.Finally,the circuit is designed and made,and the performance of the circuit is verified by actual testing experiment.(2)Existing FRI sampling kernels are analyzed and compared.The single channel FRI sampling scheme based on Fourier coefficients is studied and a method of approximating the kernel by analog low-pass filter is proposed.Filter parameters constraint conditions under perfect signal reconstruction are analyzed theoretically,according to which the sampling kernel is designed.Performance of designed kernel is verified by simulation experiment and after that the sampling kernel circuit is made.(3)According to the actual ultrasonic testing signal,a finite length signal FRI sampling method is proposed,and analyzed in theory.Then,the ultrasonic signal FRI sparse sampling system is designed,and the FRI sampling of the ultrasonic signal is realized on the hardware.(4)It is shown that the system can realize the FRI sparse sampling of ultrasonic signal by the practical application in ultrasonic detection of pipeline.In the case of ultrasonic signal with a center frequency of 5 MHz,the normal sampling method requires sampling at a rate of about 20 MHz,while the FRI sampling system designed in this thesis can accurately reconstruct the original signal with a sampling rate of 1.1 MHz,which is only 5.5% of normal sampling,greatly reducing the signal sampling frequency and the amount of sampling data.