What Is the Difference Between Analog and Digital Signals?

An analog signal refers to information represented by a continuously changing physical quantity. The amplitude, frequency, or phase of a signal changes continuously over time, or the characteristic amount of the representative information can be presented at any instant as a continuous time interval. Any value signal.

Analog signals refer to information expressed by continuously changing physical quantities, such as temperature, humidity, pressure, length, current, voltage, and so on. We usually call analog signals continuous signals, which can be infinite in a certain time range. Multiple different values. Digital signals are discrete and discontinuous signals.

Various physical quantities in actual production and life, such as images taken by cameras, sounds recorded by voice recorders, pressures, flow rates, rotational speeds, humidity, etc. recorded in the workshop control room are analog signals. Digital signals are formed by sampling, quantizing, and encoding on the basis of analog signals. Specifically, sampling is to get the input analog signal at appropriate time intervals to obtain the sample values at various times. Quantization is to use the binary code system to represent the measured values at each time after sampling, and encoding is to t The generated binary numbers are arranged together to form a sequential pulse sequence.

In the process of analog signal transmission, the information signal is first converted into an almost "identical" fluctuating electrical signal (hence the name "analog"), and then transmitted by wired or wireless means. After the electrical signal is received, it is restored to Information signal.

For nearly one hundred years, whether it is a wired telephone or a radio and television broadcast, the analog signal is used to transmit the signal for a long time. It is said that the analog signal is almost "identical" to the original signal in the waveform, and it seems that it should achieve a good propagation effect. However, the opposite is true. In the past, we often encountered inaudible and loud noise when calling; The sound of the symphony always sounds a little bigger than listening to a live band; there are also snowflakes on the TV image. This is because the signal undergoes a lot of processing and transmission during the transmission process. These devices will inevitably generate some noise and interference. In addition, if it is wired transmission, the electrical equipment near the line will also generate electromagnetic interference; if it is wireless transmission, then Even more "open", all kinds of interference in the air cannot be resisted. These interferences can easily cause signal distortion and also bring some noise. These distortions and additional noise also accumulate as the transmission distance increases, which seriously affects the communication quality. In this regard, people think of many ways. One is to take various measures to resist interference, such as improving the quality of information processing equipment and minimizing the noise it generates; adding shielding to transmission lines; and using FM carriers instead of AM carriers. However, none of these methods can fundamentally solve the problem of interference. Another method is to try to remove the noise in the signal and recover the distorted signal. However, for the analog signal, because the original undistorted signal cannot be accurately inferred from the distorted signal, this method is very It is difficult to be effective, and some even get worse.

Analog signals are mainly related to discrete

The conversion of analog signals into digital signals requires four basic steps: signal sampling, signal holding, signal quantization, and signal encoding.

The main advantage of analog signals is their precise resolution, which ideally has infinite resolution. versus

The main disadvantage of an analog signal is that it is always affected by noise (undesirably random values in the signal). The effects of these random noises can become significant after the signal is duplicated multiple times or transmitted over long distances. In electricity, these negative effects can be alleviated to some extent by using a grounded shield (shield), good line contact, and the use of coaxial cables or twisted pairs.

Noise effects can be detrimental to the signal. Lost analog signals are almost impossible to be restored again, because the amplification of the desired signal will simultaneously amplify the noise signal. If the difference between the noise frequency and the frequency of the desired signal is large, you can filter out noise at a specific frequency by introducing an electronic filter, but this solution can only reduce the impact of noise as much as possible. Therefore, under the action of noise, although the analog signal theoretically has infinite resolution, it is not necessarily more accurate than the digital signal.

Although digital signal processing algorithms are relatively complex, existing digital signal processors can quickly accomplish this task. In addition, the gradual popularization of computers and other systems has made the propagation and processing of digital signals more convenient. Devices such as cameras are gradually becoming digitized, although they must initially receive real physical information in the form of analog signals, and eventually they are converted to digital signals by analog-to-digital converters for easy processing by computers or transmission via the Internet. ^[2]