Lecture 4 : Physical Interpretation of Voltage & Current Solution
Characteristic Impedance of Transmission Line
Substituting the voltage and current solutions in the differential equations, and noting that the equations
must be satisfied by two waves indepentely we get,
We define a parameter called the 'Characteristic Impedance' of the line as
Note
The ratio of Forward Voltage and Current waves is always , and the ratio of the Backward Voltage and
Current waves is always .
The parameters and completely define the voltage and current behaviour on a transmission line.
These two parameters are related to R, L, G, and C, and the frequency of the signal. In transmission line analysis
knowledge of and is adequate and the explicit knowledge of R, L, G, C is rarely needed.
, and the ratio of the Backward Voltage and
Current waves is always 
. 
and 
completely define the voltage and current behaviour on a transmission line.
These two parameters are related to R, L, G, and C, and the frequency of the signal. In transmission line analysis
knowledge of 
and 
is adequate and the explicit knowledge of R, L, G, C is rarely needed. 
