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Microstrip formula for non-standard geometry

Discussion in 'Electronic Design' started by Wimpie, Aug 26, 2008.

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  1. Wimpie

    Wimpie Guest

    Hello,

    Most formulas for microstrip transmission line assume that there is
    dielectric all over the ground plane.

    Does somebody know a formula (or graphical solution) for the
    characteristic impedance of a microstrip where there is only
    dielectric material under the strip (so you can see the ground
    plane)?

    Best regards,

    Wim
    PA3DJS
    www.tetech.nl
    The mail address is valid when you remove abc
     
  2. qrk

    qrk Guest

    http://atlc.sourceforge.net/
    The above link is a wonderful arbitrary solver for transmission lines.
    This is primarily a Unix program. If you need a Windows build of the
    program, I probably have version 4.4 somewhere.
     
  3. Wimpie

    Wimpie Guest

    Hello Mark,

    This is good one (I found it via google also). You can enter both
    metallics and dielectrics as you want. It would be very nice when you
    can mail me a Windows Build (I hope it is not that big). A link would
    also be useful.

    My address is valid when you remove abc.

    Best regards and thanks,

    Wim
    PA3DJS
    www.tetech.nl
     
  4. JB

    JB Guest

    AFAIK dielectric between the strip and GP is the most significant unless
    stripline is to couple to other stuff. Anytime you change board material
    there are subtle changes in VF. For proto, I always like to allow for
    trimming where it has to be critical, but best to make it less critical so
    you don't have to spend time on every board. Air is better, but spacing
    variations come into play, and what will happen if you drop it. The
    calculations only get you so far unless you have your constants handy.
     
  5. John Smith

    John Smith Guest

    This is a bit off topic in direct relation to your post; however, I
    built this antenna as an external to my wifi router/switch to increase
    coverage of the net:

    http://www.centurion.com/home/pdf/wp_omni_wireless.pdf

    Fig. 1-5 and the plot of the radiation pattern (fig. 1-7) I found
    particularly interesting ...

    Regards,
    JS
     
  6. qrk

    qrk Guest


    I will keep this on the web site for a few days. About 3MB download.
    http://qrkwiggles.googlepages.com/atlc-4.4.4_Win32.zip

    This version has problems with muliple dielectrics. I works fine with
    two dielectrics, air and one of your choosing.
     
  7. Joerg

    Joerg Guest

    Thanks for sharing this, Mark. I'll try it out as well, just not right now.
     
  8. Wimpie

    Wimpie Guest

    Hello Mark,

    I received a windows build via Tom and created a .bmp file with the
    structure (with MSPaint, save as .bmp, not .jpg). Result is OK (I
    use Win2000 SP4). My hand calculation closely matches the simulated
    result.

    As long as ground (green color) surrounds your structure completely,
    results are OK. If not (for example a real microstrip line), results
    are unreliable.

    I will make the line and check the VSWR with 50 Ohms termination.

    Best regards,

    Wim
    PA3DJS
    www.tetech.nl
    when you remove abc, the address is valid.
     
  9. K7ITM

    K7ITM Guest

    The version I have, which I sent to Wim, is 4.6.0. I'm not sure about
    the differences, but if anyone is interested, I have it in a zip file
    I can send. The zip file is encrypted, so it will pass through at
    least some of the email filters that take out executables or zips with
    embedded executables; I'll supply the password of course (just my
    call...).

    Cheers,
    Tom
     
  10. qrk

    qrk Guest

    4.6.0 is the latest version which fixes the multiple dielectric
    problem. I believe this version is had multiple processor support
    removed since the author had problems getting it running properly.

    Where did you get the Windows build from? My work colleague was the
    last one to supply Dr. Kirkby a windows build which was ver 4.4.4. It
    would be great if you could give Dr. Kirkby the latest windows build
    so he can post it.
     
  11. K7ITM

    K7ITM Guest

    Ah, OK; I thought from the atlc website that we'd just all be on our
    own to do it. I'm an analog guy; I enlisted the help of a digital/
    software friend. He had no trouble building it to run in a DOS
    shell. I'll drop David a note, letting him know that I have it, to
    see if he'd like it there.

    Cheers,
    Tom
     
  12. JeffM

    JeffM Guest

    Note to Tom:
    If you are going to continue to post via Google, you should read this:
    http://groups.google.com/group/sci....gle.blockquotes.them+long-links+get.butchered
    Pursuing this via Google,
    http://www.google.com/search?q=+atlc++Win32+-4.4.4+mdtlc
    (Why they won't give you, by default, WHAT YOU ASK FOR
    http://www.google.com/search?q=atlc+Win32+-4.4.4
    really pisses me off.)

    Anyway, I discovered !!!
    http://www.google.com/search?q=cach...tiple.Dielectric.Transmission.Line.Calculator
     
  13. TheM

    TheM Guest

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