本文選題：非均勻采樣 + 信號(hào)重建��； 參考：《電子科技大學(xué)》2017年碩士論文

【摘要】：隨著現(xiàn)代電子信息技術(shù)的快速發(fā)展,信號(hào)高速采樣的應(yīng)用越來(lái)越廣泛。例如在寬帶測(cè)試系統(tǒng)、雷達(dá)、遙測(cè)遙感、圖像處理、寬帶模擬IC等方面都需要用到高速數(shù)據(jù)采集系統(tǒng)。但根據(jù)奈奎斯特原理,要想完全無(wú)損地重建信號(hào),采樣頻率至少是信號(hào)頻率的兩倍以上。實(shí)際上,在高速信號(hào)領(lǐng)域,單片的ADC并沒有達(dá)到如此高的采樣率。于是在20世紀(jì)80年代,一些研究學(xué)者提出的時(shí)間交織采樣結(jié)構(gòu)有效地解決了這個(gè)問(wèn)題,多通道并行采樣系統(tǒng)就是采用多片低速ADC形成的時(shí)間交織結(jié)構(gòu)對(duì)信號(hào)進(jìn)行采樣,并在后端進(jìn)行組合,從而實(shí)現(xiàn)了對(duì)信號(hào)的高速采樣。實(shí)際的TIADC(Time-interleaved Analog-to-digital Converter)系統(tǒng)由于各個(gè)通道間的失配誤差(偏置誤差、增益誤差、時(shí)間誤差)的存在,使得采樣后的信號(hào)形成了非均勻采樣波形,并引入了雜亂頻譜。因此要想完全重建信號(hào),首先要對(duì)信號(hào)之間的失配誤差進(jìn)行估計(jì),然后對(duì)這些誤差進(jìn)行有效地校準(zhǔn)。本文主要是從通道誤差估計(jì)和誤差校準(zhǔn)兩個(gè)方面來(lái)進(jìn)行研究,考慮到現(xiàn)有的方法多少都有一些不足,因此本文對(duì)失配誤差中的估計(jì)和校正算法都進(jìn)行了改進(jìn),進(jìn)行了更加深入的研究。(1)對(duì)失配誤差的估計(jì)進(jìn)行了改進(jìn)。經(jīng)典的正弦擬合法在進(jìn)行誤差估計(jì)的時(shí)候,大多需要事先知道信號(hào)的頻率。而在大多數(shù)應(yīng)用中,信號(hào)的頻率是無(wú)法準(zhǔn)確得知的。因此,本文對(duì)失配誤差的估計(jì)進(jìn)行了“兩步分解”。首先,采用基于相位差的快速傅里葉變換對(duì)信號(hào)的頻率進(jìn)行了精確的估計(jì),再采用經(jīng)典的正弦擬合法對(duì)信號(hào)進(jìn)行失配誤差的估計(jì)。將這兩種算法結(jié)合,這樣就可以在無(wú)需知道信號(hào)頻率的情況下,也可以對(duì)信號(hào)進(jìn)行精準(zhǔn)的失配誤差估計(jì)。(2)對(duì)時(shí)基誤差的校準(zhǔn)采用了三次樣條插值法,并且根據(jù)采樣后信號(hào)形成的周期特性,對(duì)運(yùn)算進(jìn)行了簡(jiǎn)化。在采樣只存在時(shí)基誤差的情況,對(duì)三次樣條插值法進(jìn)行信號(hào)重建做了詳細(xì)的闡述說(shuō)明,利用形成的周期非均勻采樣的周期性對(duì)三次樣條插值法進(jìn)行了改進(jìn),降低了運(yùn)算的復(fù)雜度。對(duì)分?jǐn)?shù)延遲濾波器進(jìn)行信號(hào)重建做了理論推導(dǎo),并對(duì)比三次樣條插值法和分?jǐn)?shù)延遲濾波器法。為了證明改進(jìn)后算法的有效性,本文采取了matlab仿真驗(yàn)證。仿真結(jié)果表明,使用兩種算法結(jié)合,對(duì)于通道失配誤差的估計(jì)是可行的,并且誤差估計(jì)精度較高。而在信號(hào)重建方面,改進(jìn)后的三次樣條插值法在無(wú)雜散動(dòng)態(tài)范圍和信噪比等關(guān)鍵指標(biāo)方面得到明顯提升。
[Abstract]:With the rapid development of modern electronic information technology, the application of high-speed sampling signal is more and more extensive. For example, high-speed data acquisition systems are needed in wideband test system, radar, remote sensing, image processing, broadband analog IC and so on. But according to the Nyquist principle, the sampling frequency is at least twice as high as the signal frequency if the signal is to be reconstructed completely without loss. In fact, in the field of high-speed signals, the single-chip ADC does not achieve such a high sampling rate. Therefore, in the 1980s, some researchers put forward a time-interleaved sampling structure to effectively solve this problem. The multi-channel parallel sampling system uses the time-interleaved structure formed by multi-chip low-speed ADC to sample the signal. And the combination in the back end, so as to achieve the high-speed sampling of the signal. Because of the mismatch error (bias error, gain error, time error) between the various channels, the sampled signal forms the non-uniform sampling waveform and introduces the clutter spectrum in the actual TIADC(Time-interleaved Analog-to-digital conversion system. Therefore, in order to reconstruct the signal completely, we must estimate the mismatch error between the signals, and then calibrate these errors effectively. In this paper, the channel error estimation and error calibration are mainly studied. Considering that there are some shortcomings in the existing methods, the estimation and correction algorithms of mismatch errors are improved in this paper. The estimation of mismatch error is improved. The classical sinusoidal fitting method needs to know the frequency of the signal in advance in error estimation. In most applications, the frequency of the signal is unknown. Therefore, the estimation of mismatch error is decomposed by two steps. Firstly, the fast Fourier transform based on phase difference is used to estimate the frequency of the signal accurately, and then the classical sinusoidal fitting method is used to estimate the mismatch error of the signal. By combining these two algorithms, we can use cubic spline interpolation method to calibrate the time-base error without knowing the frequency of the signal, and to estimate the mismatch error of the signal accurately. The operation is simplified according to the periodic characteristic of the sampled signal. When sampling has only time base error, the cubic spline interpolation method is explained in detail, and the cubic spline interpolation method is improved by using the periodicity of periodic nonuniform sampling. The computational complexity is reduced. The signal reconstruction of fractional delay filter is theoretically deduced and compared with cubic spline interpolation method and fractional delay filter method. In order to prove the effectiveness of the improved algorithm, matlab simulation is adopted in this paper. The simulation results show that it is feasible to estimate the channel mismatch error with the combination of the two algorithms, and the accuracy of the error estimation is high. In the aspect of signal reconstruction, the improved cubic spline interpolation method has been improved obviously in terms of the non-spurious dynamic range and signal-to-noise ratio (SNR).
【學(xué)位授予單位】：電子科技大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類號(hào)】：TN911.7

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