什么叫模拟信号什么叫数字信号（W...

什么叫模拟信号什么叫数字信号（What is analog signal What is
called a digital signal）
What is called analog signal? Take telephone as an example to explain. In telephone communication, the transmitted information is the voice of the speaker. Sound is produced by vibration. The acoustic transmitter (converter) electrical signals into sound intensity change following changes, because the signal is analog sound changes, so called "analog signal". The analog signal through the circuit (channel) transmitted to the other side, and then through the receiver (Reverse Converter) into the original sound, as if heard (sink).
The characteristic of analog signal is that it continuously "analog" the change of information, the waveform of the signal is continuous in time, so it can be called "continuous signal"". The original signals of telephone, fax and television are analog signals. Communication with analog signals is called analog communications".
What is "digital signal"? This can be illustrated by telegraph communication. The early Morse telegraph, the telegraph signal, was coded by dots and strokes (called the Morse code) to represent words and numbers. If there is an electric current representing "1" and "no current" Representing "0", then "point" is 1 and 0, and "Ji" is 1, 1, 1, 0. The Morse code is a little dash on behalf of A, by a stroke three on behalf of B, so A is 101110, B is 1110101010.......
Digital signal is a digital form of signal, its characteristics are discrete, discontinuous. Communication with digital
signals is called digital communication. The input and output signals of modern computers and the signals they are processing are discrete signals, which are very high speed digital signals. So the communication between computers is also digital communication.
Digital communications can transmit symbols, numbers, data and other digital signals. It can also transmit analog signals such as voice and image after digital processing. The process of converting analog signals into digital signals is called "analog to digital conversion"; on the contrary, the process of converting digital signals into analog signals is called "digital to analog conversion"".
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The difference between digital and analog 2008-03-22 22:30
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Analog circuit involves weak signal, but the threshold level of digital circuit is higher, and the requirement of power supply is lower than analog circuit. In the system of digital circuit and analog circuit, the noise produced by digital circuit will affect analog circuit, and make the small signal index of analog circuit become worse, and the solution is to separate analog and digital.
For the low frequency analog circuit, in addition to bold and shorten the ground, each part of the circuit using one point grounding is the best choice to suppress ground disturbance, mainly to prevent mutual interference caused by ground public impedance components.
While for the high frequency circuit and digital circuit, due to the influence of inductance effect ground will be greater at one point grounding wire extension will lead to actual and adverse effects, it should adopt separate grounding and grounding point combination.
In addition to the high frequency circuit also consider how to suppress the high frequency noise, method is: try bold wire, to reduce noise on the ground impedance; full grounding, except that printed line transmission signals, the other part as the ground. Do not have useless large area copper foil.
The ground wire should form a loop to prevent the generation of high frequency radiated noise, but the area of the loop must not be too large, so as to avoid the induction current when the instrument is in a strong magnetic field. But if it is only a low frequency circuit, the ground loop should be avoided. Digital power and analog power are best isolated and ground wires are arranged separately. If there is A/D, only one point is common here. There is not much effect in low frequency, but it is recommended to simulate and digital one point grounding. At high frequencies, the magnetic field can be simulated and digitally ground together.
If a large area of analog and digital directly connected, will lead to mutual interference. There are four ways to solve this problem: 1. Connect with magnetic beads; 2, connect with capacitor; 3, connect with inductance; 4, connect with 0 ohm resistance.
The equivalent circuit of magnetic equivalent bandstop limiter,
only to a certain frequency of the noise is significantly inhibited by pre estimated noise frequency need to use in order to choose the appropriate model. For frequency uncertainty or unpredictable conditions, magnetic beads are incompatible.
The capacitor passes through the intersection, resulting in floating ground.
The inductance is large, spurious parameters are many and unstable.
The 0 ohm resistance is equivalent to a narrow current path, which can effectively limit the loop current and make the noise be suppressed
System. Resistance is attenuated in all frequency bands (0 ohm resistance also has an impedance), which is stronger than magnetic beads.。