# Where does the origin lie in the Transmission line equation

1. Feb 20, 2013

### iVenky

Transmission line equation is of the form-

Φ(x, t) = F(x − ct) + G(x + ct)

where F(x-ct) is the forward travelling wave and
G(x+ct) is the reverse travelling wave

'x' is the distance from the origin. Now my question is where does the origin lie? Usually in Transmission lines we assume that origin lies in the load (right side) but if we see this equation it looks as if the origin lies in the source (generator) side in accordance with the wave equation.

2. Feb 20, 2013

### rbj

origin can be wherever (on the line) you care to put it.

usually i see it at the left terminus of the line and x=L at the right terminus. usually, at the left is the driving voltage source (with an internal impedance) and at the right is the load impedance. that will affect what F() and G() are.

3. Feb 21, 2013

### iVenky

Thanks for the reply. But I would like to know if I was correct or not. In the above equation that I had mentioned if F() is the forward propagation wave then it should mean that the voltage source is the origin, right?

Thanks a lot