Open Circuit Impedance Parameters (Z-Parameters):
The impedance parameters represent the relation between the voltages and the currents in the two- port network.
The impedance parameter matrix may be written as
Z11 and Z12 can be calculated by Open circuit at Port-2 side then I2 becomes zero
Z21 and Z22 can be calculated by Open circuit at Port-1 side then I1 becomes zero
In this matrix equation, it is easily seen without even expanding the individual equations, that
It can be seen that Z-parameters correspond to the driving point and transfer impedances at each port with the other port having zero current (i.e., open circuit). Thus, parameters are referred to as the open-circuit parameters.