Understand the reasons for impedance matching of PCB circuit board 2021-10-07

With the rapid development of signal transmission , It makes it easier for reflection to occur in the process of signal transmission 、 Signal integrity problems such as crosstalk , And the faster the transmission rate , The greater the signal loss . How to solve these signal integrity problems is PCB Great challenges in the rapid development .

Impedance matching refers to a suitable match between the signal source or transmission line and the load . Adjusting load power and restraining signal reflection are two main functions of impedance matching . These two functions are explained in detail below ：

1. Adjust the load power

It is assumed that the excitation source has been determined , Then the power of the load is determined by the impedance matching degree of the two . For an idealized pure resistance circuit or low frequency circuit , Basically, the inductance can be ignored 、 Reactance value caused by capacitance , At this point, the resistance becomes the main source of circuit impedance .

2、 Suppress signal reflection

A simple common sense , When a beam of light from the air shoots into the water, it will be reflected , This is because light and water have different photoconductive properties . alike , If the characteristic impedance on the transmission line changes suddenly during signal transmission, reflection will also occur . The wavelength is inversely proportional to the frequency , The wavelength of the low-frequency signal is much larger than the length of the transmission line , Therefore, the reflection problem is generally not considered . High frequency domain , When the wavelength of the signal and the length of the transmission line are of the same order of magnitude, the reflected signal is easy to overlap with the original signal , Affect signal quality . Impedance matching can effectively reduce 、 Eliminate high frequency signal reflection .

The above is pcb Reasons for impedance matching , I hope it will be of some help to you .

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