*1 Characteristic impedance
The characteristic impedance is one of the characteristics of a transmission line (e.g., board trace, coaxial cable).
The general expression of the characteristic impedance of a transmission line is Z_0=√(L/C), where L is the inductance per unit length and C is the capacitance per unit length. The unit of characteristic impedance is ohm (Ω). When a termination resistor of 50 Ω is connected to the end of a transmission line with a characteristic impedance of 50 Ω, signal reflection does not occur at the connection point.
However, if the characteristic impedance does not match the resistor value, signal reflection occurs at the connection point.