發(fā)布時間：2018-04-28 16:58

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

【摘要】：隨著現(xiàn)代電子信息技術的快速發(fā)展,信號高速采樣的應用越來越廣泛。例如在寬帶測試系統(tǒng)、雷達、遙測遙感、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,要想完全無損地重建信號,采樣頻率至少是信號頻率的兩倍以上。實際上,在高速信號領域,單片的ADC并沒有達到如此高的采樣率。于是在20世紀80年代,一些研究學者提出的時間交織采樣結構有效地解決了這個問題,多通道并行采樣系統(tǒng)就是采用多片低速ADC形成的時間交織結構對信號進行采樣,并在后端進行組合,從而實現(xiàn)了對信號的高速采樣。實際的TIADC(Time-interleaved Analog-to-digital Converter)系統(tǒng)由于各個通道間的失配誤差(偏置誤差、增益誤差、時間誤差)的存在,使得采樣后的信號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,首先要對信號之間的失配誤差進行估計,然后對這些誤差進行有效地校準。本文主要是從通道誤差估計和誤差校準兩個方面來進行研究,考慮到現(xiàn)有的方法多少都有一些不足,因此本文對失配誤差中的估計和校正算法都進行了改進,進行了更加深入的研究。(1)對失配誤差的估計進行了改進。經典的正弦擬合法在進行誤差估計的時候,大多需要事先知道信號的頻率。而在大多數(shù)應用中,信號的頻率是無法準確得知的。因此,本文對失配誤差的估計進行了“兩步分解”。首先,采用基于相位差的快速傅里葉變換對信號的頻率進行了精確的估計,再采用經典的正弦擬合法對信號進行失配誤差的估計。將這兩種算法結合,這樣就可以在無需知道信號頻率的情況下,也可以對信號進行精準的失配誤差估計。(2)對時基誤差的校準采用了三次樣條插值法,并且根據(jù)采樣后信號形成的周期特性,對運算進行了簡化。在采樣只存在時基誤差的情況,對三次樣條插值法進行信號重建做了詳細的闡述說明,利用形成的周期非均勻采樣的周期性對三次樣條插值法進行了改進,降低了運算的復雜度。對分數(shù)延遲濾波器進行信號重建做了理論推導,并對比三次樣條插值法和分數(shù)延遲濾波器法。為了證明改進后算法的有效性,本文采取了matlab仿真驗證。仿真結果表明,使用兩種算法結合,對于通道失配誤差的估計是可行的,并且誤差估計精度較高。而在信號重建方面,改進后的三次樣條插值法在無雜散動態(tài)范圍和信噪比等關鍵指標方面得到明顯提升。
[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).
【學位授予單位】：電子科技大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：TN911.7

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本文編號：1816115