In a circuit board, if there is signal transmission, it is hoped that it can be smoothly transmitted from the sending end of the power supply to the receiving end with minimal energy loss, and the receiving end will completely absorb it without any reflection. To achieve this transmission, the impedance in the line must be equal to the impedance inside the emitting end in order to be called "impedance matching". Impedance matching is one of the design elements when designing high-speed PCB circuits. The impedance value has an absolute relationship with the wiring method. For example, whether to walk on the surface layer (Microstrip) or the inner layer (Stripline/Double Stripline), the distance from the reference power layer or stratum, the wiring width, PCB material, etc. all affect the characteristic impedance value of the wiring. That is to say, the impedance value can only be determined after wiring, and there are also slight differences in the characteristic impedance produced by different PCB manufacturers. General simulation software may not be able to consider some impedance discontinuous wiring situations due to the limitations of the circuit model or the mathematical algorithms used. In this case, only some terminals (such as series resistors) can be reserved on the schematic diagram to alleviate the effect of impedance discontinuity in the wiring. The real fundamental solution to the problem is to pay attention to avoiding impedance discontinuity when wiring.