Where does the origin lie in the Transmission line equation

AI Thread Summary
The discussion centers on the origin in the transmission line equation, Φ(x, t) = F(x − ct) + G(x + ct), where F represents the forward traveling wave and G the reverse traveling wave. There is a debate about whether the origin should be placed at the load side or the source side of the transmission line. Typically, the origin is considered at the left terminus where the voltage source is located, while the load is at the right terminus. This positioning affects the functions F and G in the equation. Ultimately, the origin can be defined at any point along the line as needed for analysis.
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Transmission line equation is of the form-

Φ(x, t) = F(x − ct) + G(x + ct)

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

Thanks in advance.
 
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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.
 
rbj said:
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.


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
 
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