Referred to as PCM (pulse code modulation), i.e. pulse code modulation.
The digital signal is a continuously varying analog signal is sampled, quantized and coded generated such electrical signals as digital baseband digital signal generated by PCM terminal electric machine. It simply is analog / digital converter.
Analog signal through sampling and quantization after a series of output can be obtained, which share the Q level state. When Q is relatively large, if the Q-ary direct transmission signal, which will be the anti-noise performance is poor, therefore, usually by an encoder at the transmitting end the Q-ary signal into k-bit binary digital signal. In the receiving end the received symbols through binary decoder further reducing the Q-ary signal, such a system is Pulse Code Modulation (PCM) system. Briefly, after converting the signal into quantized code encoding process is referred to, which is called an opposite decoding process. Encoding not only for communication, but also widely used in computers, digital instruments, remote telemetry and other fields. The method of coding is varied, in the conventional coding method, if the encoding rate according to points, can be divided into two categories: low-speed and high-speed encoding encoding. Second communication type is generally used. Type encoder can be attributed to a generally three types: a successive approximation (feedback) type, a folded cascode type, mixed type. PCM binary code generally used. For quantization level Q, may be represented by the k-bit binary code, wherein each of said combination of a code word. It may generally all the quantized quantization step, lined up according to their order of some of the quantization levels, and lists each corresponding code word, while the whole of this correspondence is called pattern. Commonly used in the PCM natural binary code pattern, and the reflected binary code folding binary code (also known as the Gray code). Fold line 13 in the conventional method, in general, are by polar code, and the code sequence of segments in the paragraph code bits of the code arrangements. Whether the input signal is positive or negative, are by fold line segment 8 (paragraph 8) encoding. If the 8-bit binary code to represent the folded quantized sample value of the input signal, which represents a quantized value with a first polarity, the remaining 7 (the second to eighth bits) indicates the absolute size of the sample may be quantized values . Specifically: in 8 possible states of the second to fourth bits (code paragraph) to represent the eight paragraphs, the other four yards (inner code segments) 16 to represent the possible states of each paragraph 16 quantization level divided evenly. The encoding method is compressed, quantized and encoded into one process.
Reproduced in: https: //www.cnblogs.com/allengaller/articles/1671852.html