Research On Testing Techniques Of High-speed Nyquist Analog-to-Digital Converter's Frequency-Domain Characteristics

High-speed Nyquist Analog-to-digital converter (ADC) plays a very important role in the field of signal and informtion processing. The frequency-domain characteristics of high-speed Nyquist ADC become the focus in many ADC application fields. The frequency-domain characteristics parameters testing techniques of high-speed Nyquist ADC can be subdivided into two types, one is based on coherent sampling mode, and another is based on incoherent sampling mode.Although the precision of frequency-domain characteristics testing technique based on coherent sampling mode is very high, it requires complex expensive high-performance specialized test system to achieve and stably maintain the coherent sampling condition in the testing process. This kind of test system is difficult to build, and testing cost is very high. When the testing signal frequency is unknown or uncertainly known, the testing technique based on coherent sampling mode cannot be adopted. In contrast, the testing technique based on incoherent sampling mode is more practical and the testing cost is much lower. But this kind of testing technique needs to overcome spectral leakage and DFT/FFT fence effect caused by incoherent sampling. In addition, it needs to precisely estimate the frequency, when the input testing signal frequency is unknown or uncertainly known. To achieve these purposes, the dissertation does some reasearches on the frequency-domain characteristics testing technique based on incoherent sampling mode, and are of theoretic and practical significance.The dissertation analyses the noise estimation and frequency-domain characteristics parameters of ADC test in coherent sampling mode, and gives reasons why the results from coherent sampling mode are taken as the standard reference value for other testing techniques.ADC output signal in incoherent sampling mode weighted with window function can reduce spectral leakage to some extent, and the reduced effect has a lot to do with window function's performance. The dissertation researches combined cosine window functions. In light of the general principles of window function optimization, and considering the continuity of combined window functions and their n-oder derivatives at the two boundary points, the dissertation researches the optimization of window functions'coefficients, and proposes Maximum Side Lobe Decay improved combined cosine window function (MSLD window function), and deduces general equations of different orders of MSLD and gives the 2 to 8-term concrete MSLD window functions.The dissertation deduces and proves the general analytical equations of the peak signal gain, the peak signal power gain, the noise power gain and the equivalent noise band width of combined window functions and their squared functions, and the maximum scalloping loss of combined window functions. These analytical equations build rigorous mathematical relationship between the characteristics of combined cosine window functions and their coefficients, can overcome the shortcomings of numerical methods in the previous literature. These findings are beneficial to further researches on high-speed Nyquist ADC frequency-domain characteristics test based on incoherent sampling mode.The dissertation researches the impact of window function on ADC testing signal frequency requirement and noise estimation in incoherent sampling mode. Weighting window function to the signal can cause energy loss. Based on the principle of conservation of energy in time domain and frequency domain, the dissertation deduces the relationship among discrete combined cosine window functions energy loss factor, their coefficients and normalized noise power gain NNPG.The dissertation researches high-speed Nyquist ADC testing technique in incoherent sampling mode when the testing signal frequency is unknown or uncertainly known, and solves the testing problem under these conditions. Thus it expands the applicable scope of energy technique.In the last, the dissertation puts forward a kind of design idea for economical high-speed Nyquist ADC test system and main modules design technology of the test system, and thus builds the basis of industrialization for the test system.