Research For Time Delay Estimation Algorithms Based On Linear Frequency Modulation Signal And Its Application In Liquid Detection

As the most widely used detection technology in the21st century, ultrasonic detection isapplied in a number of fields such as industrial flaw detection, medical, oil exploration, due toits nondestructive feature. Linear Frequency Modulation signal, also called Chirp signal, is avery important signal for digital signal processing, is often utilized in the ultrasonic detectionfield. Estimating the time delay of Chirp signal in the multi-path environment is an importantresearch content in detection field. So, it is important to study time delay estimationalgorithms based on Chirp signal.Chirp Signal is a non-stationary signal, so a lot of methods based on stationary signal cannot be applied directly to Chirp Signal. In that case, this paper firstly study some classicaldelay estimation algorithms, including the cross correlation method, delay estimationalgorithms based on higher-order statistics, channel modeling or Fractional Fourier transform.Besides, this paper put emphasis on discussing two delay estimation algorithms, time delayestimation algorithm based on frequency domain windowing and time delay estimationalgorithm based on time domain coherence. And these two algorithms are proposed for LFMsignal. This paper discussed the performance of these two algorithms in different environmentin theory.Besides, this paper proposed a liquid detecting system based on these two delayestimation algorithms to estimate the propagation velocity and amplitude attenuationcoefficient of different liquid media, which is an important aspect of ultrasound imagingtechnology. We built our own system in both hardware and software, and we introduced it indetail later in this paper. We carried out the actual detection, proved that these two time delayestimation algorithms proposed in this paper are effective in actual application.