# Calculating reflection coefficient

Discussion in 'Electronics Homework Help' started by Mathias, Oct 25, 2017.

1. ### Mathias

1
0
Oct 25, 2017
Hi

I have some problems with the following assignment.

https://ibb.co/mPqO5m

I have tried using the formula
refleccoeff = (Zl-Z0) / (Zl+Z0)

In question 1, I calculated the impedance of the RL circuit, which is my Zl, and then used the above equation with Z0 = 25-j0.02

In question 2, I simply calculated
refleccoeff = (5-(25-j0.02)) / (5+(25-j0.02))

It is supposed to result in one of the following:
For question 1:
0.324 angle 12.6
0.324 angle 347
0.924 angle 347
0.924 angle 12.6

For question 2:
0.831 angle 12.4
0.231 angle 35.4
0.231 angle 35.4
0.831 angle 12.4

What am I doing wrong?
Should i use smith chart instead? If yes then how?

Thank you

2. ### dorke

2,342
665
Jun 20, 2015
What you are doing wrong is you don't take into account the length of the transmission line.

You have found the coefficient at the load and source points,
they need to be recalculated at distance l, taking into account the transmission line length,l, and the alfa and beta.

And yes a smith chart may help.  