Transmission Parameters (ABCD – Parameters):
The ABCD parameters represent the relation between the input quantities and the output quantities in the two-port network. They are thus voltage-current pairs.
However, as the quantities are defined as an input- output relation. The transmission parameter matrix may be written as
A and C can be calculated by Open circuit Port-2
B and D can be calculated by short circuit port-1
In this matrix equation, it is easily seen without even expanding the individual equations, that
These parameters are known as transmission parameters as in a transmission line, the currents enter at one end and leave at the other end, and we need to know a relation between the sending- end quantities and the receiving-end quantities.