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Modified nodal analysis and transmission line

Discussion in 'Electronic Design' started by somebody, Jan 15, 2004.

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  1. somebody

    somebody Guest

    I'm trying to code circuit analysis for an ultrasonic transducer.
    The euqivalent circuit has a floating (lossy) transmission line.
    (for example Leach, IEE transactions on ultrasonics and
    ferroeelectrics...
    vol 41 1 jan 1994)
    Just can't figure out how to incorporate lossy transmission line into
    modified nodal analysis that i'm using.
    Any ideas. Maybe using controlled sourcesd as DC or transient analysis
    is
    not needed. Only steady state ac analysis.

    Jarmo
     
  2. You have lost me here. It seems that you refering to spice simulation,
    as such there is lossy transmission line as a basic component in most
    spices.

    When you say "code", are you trying to write a simulation fuction by
    hand in source code?

    Kevin Aylward

    http://www.anasoft.co.uk
    SuperSpice, a very affordable Mixed-Mode
    Windows Simulator with Schematic Capture,
    Waveform Display, FFT's and Filter Design.

    "That which is mostly observed, is that which replicates the most"
    http://www.anasoft.co.uk/replicators/index.html

    "quotes with no meaning, are meaningless" - Kevin Aylward.
     
  3. somebody

    somebody Guest

    Yes. Spice works but I need working code for optimizing.
    C++, if it does matter. I have coded analysis for usual component types.
    I just do not know how to put transmission line into node matrices.

    Jarmo
     
  4. Mac

    Mac Guest

    I believe you can break the transmission line into segments of lumped
    element stages. RLCG.

    You'll have to decide somehow on a rule for how many segments are needed.
    It should depend on the highest frequency of interest, I suppose.

    Mac
     
  5. I don't think this is the best way to simulate a line.

    However, if you are interested, the lumped method has been discussed
    in detail in this group before, e.g.
    http://groups.google.com/groups?threadm=
    http://groups.google.com/groups?threadm=

    Regards,
    Allan.
     
  6. Jarmo Raiha

    Jarmo Raiha Guest

    I have considered this. With the speed of modern PC it is a viable
    approach.
    However I have a feeling that a true transmission line is possible too.
    Well, true line or not but line with uninform complex impedance will do.
    Ofcourse I need transmission line loads at the mechinical ports too.
    I faintly remember that line can be modelled using 4 port Y matrix and
    controlled sources with the exception that DC path is broken.
    Must dig out my old RF books.


    Jarmo
     
  7. Mac

    Mac Guest

    I read the first thread, but haven't had time to read the second one yet.
    It is certainly a good resource for the OP, if he decides to go that
    route.

    Mac
     
  8. Roy McCammon

    Roy McCammon Guest

    is it operated over a narrow band? If yes, then
    there is probably an equivalent LCR circuit.
     
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