What is a TV analog signal? What is a TV digital signal? -Solutions - Huaqiang Electronic Network

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Analog data is a continuously varying value collected by a sensor, such as voltage, current, temperature, pressure, and current sounds and images in telephone, fax, radio, and television broadcasts. In an information system, if an analog signal is transmitted in a channel, it is called analog communication.

The signal waveform changes with the change of information, which is characterized by continuous amplitude (continuous meaning is that an infinite number of values ​​can be taken within a certain range of values). If the signal waveform is also continuous in time, it is called a continuous signal; if the waveform is discrete in time, it is called a discrete signal, but because its amplitude is still continuous, it is still an analog signal.

The advantages of analog signals are intuitive and easy to implement, but at the same time, they have serious drawbacks:

(1) weak anti-interference ability

The electrical signal is interfered by various noises inside the external communication system during the transmission along the line, and the noise and the signal are difficult to separate after mixing, thereby degrading the communication quality. The longer the line, the more noise is accumulated. For example, if you rip a tape or a video tape, the quality of the sound and image will be bad once every time you rip it. The reason is that.

(2) Poor confidentiality

Analog communications, especially microwave communications and wired communications, are easily eavesdropped. As long as the analog signal is received, it is easy to get the content of the communication. So what is the digital signal of the TV set?

Digital data is a discrete value obtained by sampling, quantizing, and encoding data, such as characters, graphics, audio, and video data represented by binary code in a computer. In a communication system, if a digital signal is transmitted in a channel, it is called digital communication.

The characteristic of digital signals is that the amplitude is limited to a finite value, which is not continuous but discrete.

The advantages of digital signals are:

1. Strong anti-interference ability, no noise accumulation

In analog communication, in order to improve the signal-to-noise ratio, it is necessary to amplify the attenuated transmission signal in time during signal transmission. The noise that is unavoidably superimposed in the transmission process is also amplified at the same time. As the transmission distance increases, the noise accumulates. More and more, so that the transmission quality is seriously deteriorated.

Since the amplitude of the digital signal is a finite number of discrete values ​​(usually taking two amplitudes), although it is also interfered by noise during transmission, when the signal-to-noise ratio deteriorates to a certain extent, that is, the decision regeneration is performed at an appropriate distance. The method generates a digital signal that is the same as the original transmitting end without noise interference, so that long-distance high-quality transmission can be realized.

2. Easy to encrypt

The security and confidentiality of information transmission is more and more important. The encryption processing of digital communication is much easier than analog communication. Taking the voice signal as an example, the digitally converted signal can be encrypted and decrypted by simple digital logic operation.

3. Easy to store, process and exchange

The digital signal form is consistent with the signal used by the computer, and is a binary code. Therefore, it is convenient to be networked with a computer, and it is also convenient to store, process and exchange digital signals by a computer, so that the management and maintenance of the communication network can be automated and intelligent.

4. Equipment is easy to integrate and miniaturize

Digital signals are time-division multiplexed and do not require bulky filters. Most of the circuits in the device are digital circuits, which can be implemented with large-scale and very large-scale integrated circuits, so they are small in size and low in power consumption.

5. Facilitate the formation of an integrated digital network and an integrated services digital network

With digital transmission, digital exchange can be carried out through process-controlled digital switching equipment to realize the integration of transmission and exchange. In addition, the telephone service and various non-voice services can be digitized to form an integrated service digital network.

Compared with analog signals, digital signals have many advantages, so countries are actively developing digital communications. In recent years, China's digital communications has developed rapidly and is moving in the direction of high speed, intelligence, broadband and integration.