PCB News - An article to understand the reasons for PCB impedance matching

An article to understand the reasons for PCB impedance matching

With the development of high-speed signal transmission, signal integrity problems such as reflection and crosstalk are more likely to occur during signal transmission, and the faster the transmission rate, the greater the signal loss. How to solve these signal integrity problems is a huge challenge facing the rapid development of PCB. This is also the reason why the PCB does impedance.

PCB impedance matching

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

1. Adjust the load power

Assuming that the excitation source has been determined, the power of the load is determined by the impedance matching of the two. For an idealized pure resistance circuit or low-frequency circuit, the reactance value caused by inductance and capacitance can be basically ignored. At this time, resistance becomes the main source of circuit impedance.

2. Suppress signal reflection

A simple common sense is that when a beam of light is shot from the air into the water, it will be reflected. This is because the light guide characteristics of light and water are different. Similarly, when a signal is transmitted, if a sudden change in characteristic impedance occurs on the transmission line, reflection will also occur. The wavelength is inversely proportional to the frequency, and the wavelength of the low-frequency signal is much larger than the length of the transmission line, so there is generally no need to consider the reflection problem. In the high-frequency domain, when the wavelength of the signal and the transmission line length are of the same magnitude, the reflected signal is likely to be aliased with the original signal, which affects the signal quality. Impedance matching can effectively reduce and eliminate high-frequency signal reflections.

The above is the reason why PCB does impedance matching, I hope it will be helpful to you. iPCB is a high-tech manufacturing enterprise focusing on the development and production of high-precision PCBs. iPCB is happy to be your business partner. Our business goal is to become the most professional prototyping PCB manufacturer in the world. Mainly focus on microwave high frequency PCB, high frequency mixed pressure, ultra-high multi-layer IC testing, from 1+ to 6+ HDI, Anylayer HDI, IC Substrate, IC test board, rigid flexible PCB, ordinary multi-layer FR4 PCB, etc. Products are widely used in industry 4.0, communications, industrial control, digital, power, computers, automobiles, medical, aerospace, instrumentation, Internet of Things and other fields.