# Introduction to the impedance of the FPC board

Introduction to the impedance of the FPC board

Characteristic impedance

In electronic information products such as computers and wireless communications, the energy transmitted in the circuit of the PCB is a square wave signal (called pulse pulse) composed of voltage and time, and the resistance encountered is It is called characteristic impedance.

2. Differential impedance

The driver inputs two identical signal waveforms of opposite polarity, which are respectively transmitted by two differential lines, and the two differential signals are subtracted at the receiving end. The differential impedance is the impedance Zdiff between the two wires.

3. Odd mode impedance

The impedance of the first line to the ground in the two lines is Zoo, and the impedance values of the two lines are the same.

Even mode impedance

The drive inputs two identical signal waveforms of the same polarity, and the impedance Zcom when the two wires are connected together.

4. Common mode impedance

The impedance of the first line to ground in the two lines, Zoe, the impedance values of the two lines are the same, usually larger than the odd mode impedance.