FPC factories should not wait for the PCB board to be scrapped before they realize that impedance design is so important!

1. What is impedance



FPC factory tells you that in electricity, the obstruction of current in a circuit is often referred to as impedance. The impedance unit is ohms, commonly represented by Z, and is a complex number:



Z=R+i（ ω L-1/（ ω C) )



Specifically, impedance can be divided into two parts, resistance (real part) and reactance (imaginary part).



Reactance also includes capacitive reactance and inductive reactance. The current obstruction caused by capacitance is called capacitive reactance, and the current obstruction caused by inductance is called inductive reactance.



2. An Ideal Model for Impedance Matching



Most RF engineers have encountered impedance matching issues, and FPC factories tell you that the purpose of impedance matching is to ensure effective transmission of signals or energy from the "signal source" to the "load".



The most ideal model is, of course, to have an output impedance of 50 ohms at the Source end, a transmission line impedance of 50 ohms, and an input impedance of 50 ohms at the Load end, all the way down to 50 ohms, which is the most ideal.



However, the actual situation is that the source impedance will not be 50 ohms, and the load impedance will not be 50 ohms, which requires several impedance matching circuits.



The matching circuit is composed of inductors and capacitors, and at this point, we need to use capacitors and inductors for impedance matching circuit debugging to achieve optimal RF performance.