模拟信号数字化过程（Analog signal digitization process）.docVIP

模拟信号数字化过程（Analog signal digitization process） Digitizing digital signals requires three steps: sampling, quantization, and coding. Sampling refers to replacing the original continuous signal with the signal sample sequence at regular intervals, that is, to discretize analog signals in time. Quantization is to approximate the amplitude value of the original continuous variation with a finite amplitude value, and the continuous amplitude of the analog signal is reduced to a finite number of discrete values with a certain interval. Coding is according to certain rules, the quantized values are expressed in binary digits, and then converted into two or more valued digital signal streams. The digital signals thus obtained can be transmitted through cables, microwave trunk lines, satellite channels, and other digital lines. At the receiving end, the analog signal is digitized in reverse direction, and then it is restored to the original analog signal by post filtering. The digital process is also called pulse code modulation. sampling Speech signals are analog signals, which are continuous not only in magnitude, but also in time. In order to digitize the voice signal and realize time division multiplexing, we must first discrete the audio signal in time, which is called sampling. The so-called sampling is the instantaneous amplitude value (sampling value) of the voice signals extracted at intervals of T, and a series of discrete sampling values in time are called sampling value sequences. The sampled value sequence is discrete in time and can be time-division multiplexed, and each sampling value can be quantized and encoded into binary digital signals. Theory and practice prove that as long as the sampling interval of the pulse (2fm) (T = 1/ or F = 2fm (FM) is the highest frequency of the voice signal), is sampling of the sample sequence can be reduced to no distortion of the original speech signal. For example, a telephone signal frequency is 300 ~ 3400Hz, fm=3400Hz, FS,