本文選題：Chirp　切入點(diǎn)：線性調(diào)頻信號(hào)　出處：《華南理工大學(xué)》2014年碩士論文　論文類型：學(xué)位論文

【摘要】：超聲探測(cè)作為21世紀(jì)運(yùn)用最為廣泛的探測(cè)技術(shù)，因其無(wú)損特性，被廣泛應(yīng)用于工業(yè)探傷，，醫(yī)學(xué)，石油探測(cè)等領(lǐng)域。Chirp信號(hào)(LFM，線性調(diào)頻信號(hào))是數(shù)字信號(hào)處理領(lǐng)域的一種非常重要的信號(hào)，被經(jīng)常應(yīng)用到超聲探測(cè)中。時(shí)延估計(jì)是超聲探測(cè)中的經(jīng)典問(wèn)題，該技術(shù)是超聲定位，超聲成像等超聲應(yīng)用的重要內(nèi)容。因此，對(duì)Chirp信號(hào)的時(shí)延估計(jì)算法的研究具有重要的意義。 Chirp信號(hào)是一種典型的非平穩(wěn)信號(hào)，因此目前很多針對(duì)平穩(wěn)信號(hào)的時(shí)延估計(jì)算法直接應(yīng)用到線性調(diào)頻信號(hào)上并不一定適用。在這種情況下，本文首先對(duì)經(jīng)典的時(shí)延估計(jì)算法，包括互相關(guān)法、高階統(tǒng)計(jì)矩時(shí)延估計(jì)算法、匹配濾波時(shí)延估計(jì)算法、基于信道建模的時(shí)延估計(jì)算法和基于分?jǐn)?shù)階傅里葉變換的時(shí)延估計(jì)算法等，進(jìn)行了理論學(xué)習(xí)和研究。同時(shí)，本文重點(diǎn)研究了基于頻域加窗的時(shí)延估計(jì)法和基于時(shí)域相干的時(shí)延估計(jì)算法。這兩種算法都是針對(duì)于線性調(diào)頻信號(hào)的。本文分別對(duì)以上兩種算法進(jìn)行了數(shù)學(xué)上的理論推導(dǎo)，并且通過(guò)仿真，證實(shí)了其有效性。同時(shí)，分別針對(duì)以上兩種算法在不同信噪比，不同多徑數(shù)目等不同的仿真環(huán)境下，進(jìn)行了性能的比較和分析。 在本文的最后，運(yùn)用基于頻域加窗的時(shí)延估計(jì)算法和基于時(shí)域相干的時(shí)延估計(jì)算法，實(shí)驗(yàn)團(tuán)隊(duì)搭建了一套完整的液體檢測(cè)系統(tǒng)，用于對(duì)不同液體介質(zhì)的判斷。不同的液體具有不用的傳播速率和幅度衰減系數(shù)，因此，可以由此分辨不同的液體介質(zhì)。傳播速度和幅度衰減系數(shù)都可以通過(guò)時(shí)延估計(jì)算法得到。對(duì)介質(zhì)的傳播速度，幅度衰減系數(shù)等聲參量的估計(jì)，是超聲成像技術(shù)的重要內(nèi)容。針對(duì)于我們的應(yīng)用，團(tuán)隊(duì)搭建了自己的硬件和軟件系統(tǒng)。在本文中，對(duì)基于線性調(diào)頻信號(hào)的液體檢測(cè)系統(tǒng)進(jìn)行了詳細(xì)的說(shuō)明,并且進(jìn)行了實(shí)際的探測(cè)實(shí)驗(yàn)。實(shí)驗(yàn)結(jié)果表明，本文討論的兩個(gè)時(shí)延估計(jì)算法具有實(shí)際的效用。
[Abstract]:Ultrasonic detection, as the most widely used detection technology in the 21st century, is widely used in industrial flaw detection and medicine because of its nondestructive properties. Chirp signal LFM is a very important signal in the field of digital signal processing, which is often used in ultrasonic detection. Time delay estimation is a classical problem in ultrasonic detection. Therefore, it is of great significance to study the time delay estimation algorithm of Chirp signal. Chirp signal is a kind of typical non-stationary signal, so many time delay estimation algorithms for stationary signal are not always applicable to LFM signal directly. In this case, the classical time delay estimation algorithm is firstly studied in this paper. It includes cross-correlation method, high-order statistical moment delay estimation algorithm, matched filter time delay estimation algorithm, channel model-based time delay estimation algorithm and fractional Fourier transform based time delay estimation algorithm. This paper focuses on the time-delay estimation algorithm based on windowed frequency domain and time-domain coherent time-delay estimation algorithm. Both algorithms are aimed at LFM signals. At the same time, we compare and analyze the performance of the two algorithms under different simulation environments, such as different signal-to-noise ratio (SNR) and different number of multipath. At the end of this paper, using the time-delay estimation algorithm based on frequency-domain windowing and time-domain coherent time-delay estimation algorithm, the experimental team built a complete liquid detection system. Used to judge different liquid media. Different liquids have unwanted propagation rates and amplitude attenuation coefficients, so, The propagation velocity and amplitude attenuation coefficient can be obtained by time delay estimation algorithm. The sound parameters such as propagation velocity and amplitude attenuation coefficient can be estimated. Is the important content of ultrasonic imaging technology. For our application, the team built their own hardware and software system. In this paper, the liquid detection system based on LFM signal is described in detail. The experimental results show that the two delay estimation algorithms discussed in this paper are effective.
【學(xué)位授予單位】：華南理工大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2014
【分類號(hào)】：TN911.23

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