Difference: 1 Analog signals are represented by a series of continuously changing electromagnetic waves or voltage signals; digital signals are represented by a series of intermittent changing voltage pulses (for example, we can use a constant positive voltage to represent the binary number 1, and a constant negative voltage to represent the binary number 1.

Binary number 0), or light pulse.

When an analog signal is represented by a continuously changing electromagnetic wave, the electromagnetic wave itself is both a signal carrier and a transmission medium; when an analog signal is represented by a continuously changing signal voltage, it generally passes through traditional analog signal transmission lines (such as telephone networks).

, cable television network) to transmit.

2 When digital signals are represented by intermittent changing voltages or light pulses, it is generally necessary to use twisted pairs, cables or optical fiber media to connect the two communication parties in order to transmit the signal from one node to another node.

Digital signal refers to a signal in which the independent variable is discrete and the dependent variable is also discrete. The independent variable of this signal 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. For example, a binary number with a word length of 2 bits can represent 4 sizes of digital signals, which are 00, 01, 10 and 11; if the range of the signal changes

In -1~1, these 4 binary numbers can represent 4 digital ranges, namely [-1, -0.5), [-0.5, 0), [0, 0.5) and [0.5, 1].

Since digital signals use two physical states to represent 0 and 1, their ability to resist interference from the material itself and environmental interference is much stronger than analog signals; in signal processing with modern technology, digital signals play an increasingly important role.

Large, almost complex signal processing is inseparable from digital signals; in other words, as long as the solution to the problem can be expressed in mathematical formulas, computers can be used to process digital signals representing physical quantities.

The difference between digital signals and discrete-time signals is the dependent variable.

The independent variable of a discrete time signal is discrete and the dependent variable is continuous. The independent variable is represented by an integer, and the dependent variable is represented by a number corresponding to the size of the physical quantity.

When the magnitude of a discrete-time signal is represented by a finite binary number, it is a digital signal.

For the discrete time signal x(n)=sin(0.3n), when the independent variable n=6, the dependent variable x(6)=sin(0.3×6)≈0.9738; if it is converted into a digital signal using 2-bit binary

, according to [-1, -0.5), [-0.5, 0), [0, 0.5) and [0.5, 1] ??corresponding to 00, 01, 10 and 11, it is most appropriate to use the binary number 11 to represent 0.9738.

When learning and researching digital signal theory, it is very troublesome to use binary numbers to represent signals; for convenience, people generally treat discrete-time signals as digital signals at this time, without considering the differences between them.

Since digital signals use two physical states to represent 0 and 1, their ability to resist interference from the material itself and environmental interference is much stronger than analog signals; in signal processing with modern technology, digital signals play an increasingly important role.

Large, almost complex signal processing is inseparable from digital signals; in other words, as long as the solution to the problem can be expressed in mathematical formulas, computers can be used to process digital signals representing physical quantities.

Digital signal characteristics: strong anti-interference ability, 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, that is, at the appropriate

The distance decision regeneration method is used to regenerate the same digital signal as the original sender without noise interference, so long-distance and high-quality transmission can be achieved.

Analog signals refer to information expressed by continuously changing physical quantities, such as temperature, humidity, pressure, length, current, voltage, etc. We usually call analog signals continuous signals, which can have infinite values ??within a certain time range.

Multiple different values.

Digital signals refer to signals that are discrete and discontinuous in value.

Various physical quantities in actual production and life, such as images captured by cameras, sounds recorded by tape recorders, pressure, flow, rotation speed, humidity, etc. recorded in the workshop control room are all analog signals.

Digital signals are formed by sampling, quantizing and encoding based on analog signals.

Specifically, sampling is to obtain the sample values ??at each moment from the input analog signal at appropriate time intervals. Quantization is to represent the values ??at each moment measured by sampling in binary code, and encoding is to convert t

The resulting binary numbers are arranged together to form a sequence of sequential pulses.

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 through wired or wireless means. After the electrical signal is received, it is restored to an analog signal through the receiving device.

information signal.