Equivalent terminal resistance-Impedance Matching

Impedance Matching:

 

Terminal resistance is used in communication to eliminate signal reflection in communication cables. In communication, there are two reasons for signal reflection: impedance discontinuous and impedance mismatch. The impedance is not continuous, and the signal suddenly encounters a very small or even no cable impedance at the end of the transmission line, and the signal will cause reflection in this place. The principle of this signal reflection is similar to that when light enters another media, it causes reflection. To eliminate this reflection, a terminal resistor of the same size as the characteristic impedance of the cable must be connected at the end of the cable to make the impedance of the Cable Continuous. Because the signal is transmitted in two directions on the cable, the other end of the communication cable can be connected to a terminal resistor of the same size. Another cause of signal reflection is that the impedance between the data transceiver and the transmission cable does not match. The reflection caused by this is mainly manifested in the confusion of the entire network data when the communication line is idle. To reduce the influence of the reflected signal on the communication line, noise suppression and bias resistance are usually used. In practical applications, for relatively small reflected signals, it is simple and convenient to use the method of adding bias resistance.

 

After impedance matching, the edge of the signal will not be burrs, and there will be no standing waves, because the signal will not be reflected and superimposed.

The equivalent impedance of the signal source and the load is bounded (the influence of the transmission line on the equivalent impedance should be considered), so that the load end can obtain the maximum signal energy.
Generally, the matching circuit is electrically resistant, and the impedance varies with different frequencies, so the frequency selection function is attached. However, if the entire circuit has only the resistance components (of course, this is rare), you cannot select the frequency.
After matching is met, the output end obtains the maximum energy output. The amplitude is stable, but the value of the phase shifting is variable, which is determined by the circuit structure.

 

 

Signal isolation:

 

 

On the double-row pin, the ground is located on the left and the input on the right is used as the signal line. This is done to ensure the stability of the high-speed signal line. (It is generally told that DAC and so on are all done in this way, separated by ground)

 

Just write...