Features are: 1. Strong anti-interference ability and no noise accumulation. 2. Facilitates encryption processing; the digitally transformed signal can be encrypted and decrypted using simple digital logic operations. 3. The signal form of digital communication is consistent with the signals used by computers, and they are all binary codes. Therefore, it is easy to use computers to store, process and exchange digital signals, which can make the management and maintenance of communication networks automated and intelligent. 4. The equipment is easy to integrate and miniaturize. 5. It is convenient to form an integrated digital network and an integrated service digital network. 6. The occupied channel frequency band is wider.
The operating environment of this tutorial: Windows 7 system, Dell G3 computer.
What is a digital signal
Digital signal refers to a signal in which the independent variable is discrete and the dependent variable is also discrete. The independent variable is represented by an integer and the dependent variable is represented by a number among finite numbers. In computers, the size of digital signals is often represented by binary numbers with limited bits.
Digital signals refer to using a set of special states to describe signals. Typically, signals are represented by the most common binary numbers. The fundamental reason why binary numbers are used to represent signals is that circuits can only Represents two states, namely, on and off of the circuit. In actual digital signal transmission, a certain range of information changes are usually classified as state 0 or state 1. The setting of this state greatly improves the anti-noise ability of digital signals. Not only that, in terms of confidentiality, anti-interference, transmission quality, etc., digital signals are better than analog signals, and they save more signal transmission channel resources.
Characteristics of digital signals:
1. Strong anti-interference ability and no noise accumulation. In analog communications, in order to improve the signal-to-noise ratio, the attenuated transmission signal needs to be amplified in time during the signal transmission process. The noise inevitably superimposed on the signal during the transmission process is also amplified at the same time. As the transmission distance increases, more and more noise accumulates, causing the transmission quality to seriously deteriorate.
For digital communications, since the amplitude of the digital signal has a limited number of discrete values (usually two amplitudes), although it is also interfered by noise during the transmission process, when the signal-to-noise ratio deteriorates to a certain extent At this time, the decision regeneration method is used at an appropriate distance to regenerate the same digital signal as the original transmitter without noise interference, so long-distance high-quality transmission can be achieved.
2. Convenient encryption processing. The security and confidentiality of information transmission are becoming more and more important. The encryption of digital communication is much easier than that of analog communication. Taking voice signals as an example, the digitally transformed signal can be encrypted and decrypted using simple digital logic operations.
3. Easy to store, handle and exchange. The signal form of digital communication is consistent with the signals used by computers. They are all binary codes. Therefore, it is easy to network with computers and to store, process and exchange digital signals with computers. It can make the management and maintenance of communication networks automated and intelligent.
4. The equipment is easy to integrate and miniaturize. Digital communications use time division multiplexing and do not require bulky filters. Most of the circuits in the equipment are digital circuits and can be implemented with large-scale and very large-scale integrated circuits, so they are small in size and have low power consumption.
5. It is convenient to form an integrated digital network and an integrated service digital network. Using digital transmission mode, digital exchange can be carried out through program-controlled digital switching equipment to achieve the integration of transmission and exchange. In addition, telephone services and various non-telephone services can be digitized to form an integrated service digital network.
6. The occupied channel frequency band is wider. The frequency band of one analog phone is 4kHz bandwidth, and the frequency band of one digital phone is about 64kHz. This is the main reason why analog communication still has vitality. With the extensive use of broadband channels (optical cables, digital microwaves) (a pair of optical cables can open thousands of telephone lines) and the development of digital signal processing technology (the bit rate of a digital telephone line can be compressed from 64kb/s to 32kb/s Even lower digital rates), the bandwidth problem of digital phones is no longer a major issue.
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