# Transmission lines

Discussion in 'Homework Help' started by stiltzkin23, May 10, 2013.

1. ### stiltzkin23 Thread Starter New Member

May 10, 2013
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Hi everyone. I have a little problem regarding transmission lines. I know how to calculate the input impedance of a transmission line in function of the length of the line. Now however, I have to calculate the voltage across an impedance behind a tranmission line, and I don't really know how to calculate this.

So to be clear. Consider the following circuit :

A voltage source with internal impedance, connected with an arbitrary impedance by a transmission line. How do I calculate the voltage across just the impedance (and not the combination of impedance and transmission line).

2. ### t_n_k AAC Fanatic!

Mar 6, 2009
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We don't teach transmission line theory - we might help with specific problems. Post an example if possible.

3. ### stiltzkin23 Thread Starter New Member

May 10, 2013
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Hmmm, I don't know if that'll help. My problem is actually acoustic, but it can be solved electronically just as well.

The acoustic problem is as follows. I have an earplug with a certain frequency spectrum and internal impedance. When you put this earplug in your ear, it will send the vibrations to your eardrum (= arbitrary impedance) through the ear canal (= transmission line). Now I know the frequency spectrum and internal impedance of the earplug, and I also know the impedance of the eardrum. Now I need to calculate how these two are connected.

Feb 5, 2010
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5. ### stiltzkin23 Thread Starter New Member

May 10, 2013
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Thank you for the article, but it's not really what I need. There, the impedance of the eardrum is calculated using a distributed parameter model. I already have the eardum impedance however, but I need to know how I can calculate the pressure over it, when it is behind a transmission line. I have no use for their distributed parameter model.

6. ### t_n_k AAC Fanatic!

Mar 6, 2009
5,448
782
No doubt one can use transmission line concepts for acoustic situations.

For the electrical transmission line case one needs to know various parameters of which you are presumably aware.

I would refer you to this link for the details ...

http://www.ece.rutgers.edu/~orfanidi/ewa/ch10.pdf