Advantages: The main advantage of analog signal is its accurate resolution, which is infinite in an ideal situation. Compared with digital signals, analog signals have higher information density. Because there is no quantization error, the real value of natural physical quantity can be described as close as possible.
Another advantage of analog signal is that when the same effect is achieved, analog signal processing is simpler than digital signal processing. Analog signal processing can be directly realized by analog circuit components (such as operational amplifiers), while digital signal processing often involves complex algorithms and even requires special digital signal processors.
Disadvantages: The main disadvantage of analog signals is that they are always affected by noise (unpredictable random changes in signals). After the signal is copied many times or transmitted over a long distance, the influence of these random noises may become very significant.
The noise effect will make the signal harmful. It is almost impossible to recover the lost analog signal, because the amplification of the desired signal will also amplify the noise signal.
2. Digital signal
Advantages:
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, and the noise inevitably superimposed on the signal during transmission is also amplified at the same time. With the increase of transmission distance, the noise accumulates more and more, which leads to the serious deterioration of transmission quality.
For digital communication, because the amplitude of digital signal is a finite discrete value (usually two amplitudes), although it will be disturbed by noise in the transmission process, when the signal-to-noise ratio deteriorates to a certain extent, that is, the decision regeneration method is adopted at an appropriate distance to generate the same digital signal as the original sender without noise interference, so long-distance high-quality transmission can be realized.
Convenient encryption processing
The security and confidentiality of information transmission are becoming more and more important. Encryption of digital communication is much easier than analog communication. Taking speech signal as an example, the digitally converted signal can be encrypted and decrypted by simple digital logic operation.
Easy to store, handle and exchange.
The signal form of digital communication is consistent with the signal used by the computer, and both are binary codes, which is convenient for connecting with the computer, and also convenient for the computer to store, process and exchange digital signals, which can make the management and maintenance of the communication network automatic and intelligent.
The equipment is convenient for integration and miniaturization.
Digital communication adopts time division multiplexing, which does not need large filters. Most of the circuits in the equipment are digital circuits, which can be realized by large-scale and ultra-large-scale integrated circuits, so it is small in size and low in power consumption.
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 exchange equipment to realize 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.
The occupied channel frequency band is wider.
An analog phone has a bandwidth of 4kHz, and a digital phone accounts for about 64kHz. With the wide use of broadband channels (optical cable, digital microwave) (a pair of optical cables can open thousands of telephones) and the development of digital signal processing technology (the digital rate of a digital telephone can be compressed from 64kb/s to 32kb/s or even lower), the bandwidth problem of digital telephone is no longer the main problem.
Disadvantages: the algorithm is complex.
The difference between extended data analog signal and digital signal:
The main difference between analog signals and digital signals is that one is continuous and the other is discrete.
Different data must be converted into corresponding signals before transmission:
Analog data are generally represented by analog signals, such as a series of continuously changing electromagnetic waves (such as electromagnetic waves in broadcasting) or voltage signals (such as audio voltage signals in telephone transmission);
Digital data is represented by digital signals, such as a series of intermittent voltage pulses (for example, we can use a constant positive voltage to represent binary number 1 and a constant negative voltage to represent binary number 0) or optical pulses.
When analog signals are represented by continuously changing electromagnetic waves, the electromagnetic waves themselves are both signal carriers and transmission media. When analog signals are represented by continuously changing signal voltages, they are generally transmitted through traditional analog signal transmission lines (such as telephone networks and cable television networks).
When digital signals are expressed by intermittent voltages or optical pulses, it is generally necessary to connect the two communication parties with twisted pair and optical fiber medium to transmit signals from one node to another.
References:
Baidu Encyclopedia-Digital Signal
Baidu Encyclopedia-Analog Signal