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Microstrip Length

Discussion in 'Electronic Design' started by Philip Newman, Apr 8, 2004.

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  1. How can I calculate the length of a line of microstrip, by using the
    Effective Electrical Length and it's impedance?

    I know how to calculate the width of the line, but what about the length?

    I can use ADS' LineCalc to achieve this, but I wish to find a formula. What
    formula does LineCalc use? I cannot find it anywhere.

    Assume I know all the substrate and metallisation parameters.


  2. Active8

    Active8 Guest

    Use the VP factor, 1/sqrt(e_r) where e_r is the dielectric constant
    of the substrate.

    l_phys = VP * l_elec
  3. Hmm, doesn't work for my values or consistent with LineCalc. I think I may
    be confusing Electrical Length with Phase Change.

    I looked in my Pozar Book, and found the equations. They work out fine, so
    no panick!

    Cheers anyway

  4. John Larkin

    John Larkin Guest

    Appcad reports this, based on effective dielectric constant Eef; it
    gives you Eef, too.

  5. Mac

    Mac Guest

    This doesn't work for microstrip. The deal with microstrip is that the
    effective dielectric constant is somewhere in between that of the
    dielectric medium and that of free-space (or other surrounding medium).
    This sort of makes sense if you think in terms of the field lines
    emmanating from the microstrip: some of them go through air (or other
    surrounding medium) and some of them go through the substrate.

    Pozar's book (I have _Microwave Engineering_ second edition) gives
    equations, as the OP already discovered.

  6. danesh.8


    Jan 27, 2009
    Hi Mac,

    can u share the formula that you found from pozar. chapter or the book page
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