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.
     
  4. Kermit2

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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
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    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

    About page no. 422

    I guess if you can equate the various electrical parameters to their acoustic physical equivalents in your case, then you have a possible means to a solution.
     
  7. stiltzkin23

    Thread Starter New Member

    May 10, 2013
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    That is indeed what I needed. Thank you very much!
     
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