Characteristic impedance (ZO) can be defined as: The characteristic impedance - the ratio of a pair of voltage and current waves at any point on that transmission line in the absence of reflections - may or may not be constant. It is very important to transfer radio frequency energy from a generator to a load through transmission lines with zero or minimum power loss. To achieve this, the source and the load impedances have to be matched. And the transmission line between them should have equal characteristic impedance as well (usually 50 Ω for RF transmission). We can measure the amount of reflected power by reflection coefficient (Γ) Impedance mismatch in the transmission line will cause some of the signal power reaching to the load to be reflected back and produce standing wave. The coefficient has to be as small as possible. The ideal value is zero when the load impedance is the same as the characteristic impedance. Insert impedance matching network between the source and the load.Ĭircuit representation of ZS and ZL configuration.Run computer simulation or (please explain this or else discard it.).Terminate the line with the same characteristic impedance to make the line looks infinitely long because there are no reflections coming from the end of the cable (like putting a resistor which has the same value as the ZO at the end of the transmission line).Now, we know that it’s very important to have matched impedance in RF system.

The purpose of impedance matching network is to conjugate match the source and the load. And when the load impedance is the conjugate of the source impedance, maximum power is transferred.

Two-element impedance matching networks will be discussed here.

Smith chart zy