采样率小于一个连续时间信号最大频率的2倍时就叫undersampling，欠采样，根据抽样定理，当fs>=2fmax，也就是oversampling，过采样时，数字信号才能重建成原来的模拟信号，欠采样重建会发生混叠-Sampling rate of a continuous-time signal is less than the maximum frequency of 2 times is called undersampling, bandpass sampling, according to sampling theorem, when fs
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An Overview of Sigma Delta ADCs and DAC Devices.pdf
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