antenna-theory.com

[Jostikas]

Hi!

The definition formula for characteristic impedance on http://www.antenna-theory.com/tutorial/txline/transmission2.php seems wrong to my eyes.

Z_0 = V+/I+ = -(V-/I-)

I have no problems with the first equals sign. However, the second one seems dubious. If this is correct, it would seem to imply that the sign of the characteristic impedance depends on what end of the line we look at it from. Could someone explain how this can be?

[Schubert]

It's all convention

if reflection coefficient is ZL-Z0)/(ZL+Z0) then what happens to the reflected waves for a short and open circuit? You could just as easily argue no minus sign in the equation if total_I = I+ - I- (forward wave minus reflected wave)

Anyway, the minus sign keeps things consistent