# Transmission Line Theory problem

Discussion in 'Wireless & RF Design' started by ECE101, Dec 2, 2011.

1. ### ECE101 Thread Starter New Member

Nov 25, 2011
29
0
Hi I'm having a problem arriving at the same result in this transmission line question.

Taking Beta = W/U = 2*pi*f/0.7c = (2*pi*2*10^9)/(0.7*2.998*10^-8) = 59.88

Zo = 100?
Zin = 92.3 - j67.5

Zl =
100 ( 92.3 - j67.5 -j(100)*tan(59.88*0.3) )
-------------------------------------------
( 100 - j(92.3 - j67.5)*tan(59.88*0.3))

Zl =
100 ( 92.3 + j54.844 )
------------------------
( 182.58 + j112.923)

Zl = 52.41 + j26.328

So the resistive component is roughly right however the inductive component is pretty far out.

Can anyone see where I'm going wrong?

2. ### t_n_k AAC Fanatic!

Mar 6, 2009
5,448
782
Re-check your calculations - it's just the last step

Zl = 52.41 + j26.328

that's wrong.

Everything is OK up to there.

ECE101 likes this.
3. ### ECE101 Thread Starter New Member

Nov 25, 2011
29
0
Do'h!

Serves me right for taking shortcuts with a calculator

worked it out by hand and it was fine!

Thanks t_n_k!