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RF inductors in OrCad

Discussion in 'CAD' started by yAro, Oct 16, 2006.

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  1. yAro

    yAro Guest

    Does anyone know if there any OrCad libraries
    containing flat spiral RF inductors?
    If no, then if I create an equivalent RLC circuit
    how can I simulate the dependency
    between inductance and frequency? Is it possible
    at all in this application or should I
    rather look for something else?
    yaro
     
  2. Jim Thompson

    Jim Thompson Guest

    Make it up with a .SUBCKT declaration

    Then, in Probe, look at the real and imaginary components of current
    to derive inductance variation with frequency. (Create your own
    MACRO)

    ...Jim Thompson
     
  3. yAro

    yAro Guest

    I was hoping there may be some easy way, so even
    someone who run an electronic Cad for
    the firs time can do it. So far I learned only
    some basics like building a circuit and running
    PSpice
    to get a graph showing current and voltage
    behaviour of that circuit. I've got no idea where
    to
    look for .SUBCKT or Probe however, or how to
    create macros in this application.
    My guess is that the macro will have something to
    do with using the formula for inductance where
    L=2pi*f*X and X=Vo / Io as I found only
    voltage, current and power markers in OrCad.
    If it wouldn't be to much to ask for more detailed
    explanation I would be
    very grateful as the only reason why I get my
    hands on OrCad is that I was hoping to find some
    easy
    way to simulate the relation between induction and
    frequency for different numbers of turns of a flat
    spiral coil to compare it with my measurements.
    The program looks much more complex then I thought
    and I never used any Cad applications before. I
    thought it will rather allow me to draw the
    component I
    need, giving it all the characteristics I require
    and then there will be an option to measure any
    parameters
    of that element that I need. Unfortunately it
    isn't so.
    J Celmer
     
  4. Leon

    Leon Guest

    The Pulsonix software I use has interactive spiral design support:

    Spirals using intelligent rules supported
    Circular/square shape
    Gap rules defined
    Number of turns
    Inner spiral width defined
    Aspect ration for non-square shapes
    Corner radius defined for circular shapes
    Spirals can be made in Copper and non-electrical shapes
    Spirals can be created and saved within the footprint definition

    You need other software to simulate the inductor, though.

    Leon
     
  5. You are basically using the wrong software for the job. PSpice is a
    general SPICE simulator, and CAN do RF simulation, but you have to do a
    lot of the work yourself. What you are needing is an RF specific
    simulator, that can take a spiral inductor definition and simulate it
    for various characteristics. For that, you might be better served
    looking at Microwave Office, or the Agilent tools. If you just need to
    extract a generic spice model from your spiral, Ansoft has tools that
    can do that.

    But, if you are going to do spiral inductors and other RF design, you
    are going to need CAD to get it right!

    Charlie
     
  6. yAro

    yAro Guest

    Thanks for the tip but I wan't be able to use it
    for the simulation I'd like to perform
    yaro
     
  7. yAro

    yAro Guest

    You are basically using the wrong software for
    Thanks Charlie. I checked MW Studio and from what
    I found it is only suitable
    for 2d objects and similarly like sonnet (fully 3d
    tool) which I found fallowing the path
    you suggested it doesn't use typical wires but
    micro strips which I'm not too familiar with
    and not sure if I can use them to simulate a macro
    sized inductor with them. Also I'm not sure
    what they mean by ports in both of the programs.
    Honestly, I thought I could find something
    more user friendly for old fashion electrical
    engineers rather than computer experts.
    Cheers
    yaro
     
  8. Welcome to the wonderful world of RF design. The rule is, THERE ARE NO
    WIRES! :cool: Everything is a transmission line, and there are no 'just
    connection' wires in your design.

    Charlie
     
  9. Joerg

    Joerg Guest

    Hello Charlie,
    And in RF design there is no free lunch, usually :)

    Anyway, Yaro, check this out:
    http://rfic.eecs.berkeley.edu/~niknejad/asitic.html
     
  10. Jim Thompson

    Jim Thompson Guest

    On Fri, 20 Oct 2006 00:28:00 GMT, Joerg

    [snip]
    Thanks, Joerg, Good link.

    But your newsreader quoting/snipping sucks... can't tell who said what
    when ;-)

    ...Jim Thompson
     
  11. Joerg

    Joerg Guest

    Hello Jim,
    Better?
     
  12. Jim Thompson

    Jim Thompson Guest

    Almost. Who's this "Jim" fellow you're saying "Hi" to ?:)

    ...Jim Thompson
     
  13. Joerg

    Joerg Guest

    Ahm, some guy who know a thing or two about chips and red wine :)

    So, is the "Hello" up top also not kosher on usenet? Sounds so
    non-personal not to do that but if it is customary I guess I have to
    drop it.
     
  14. Jim Thompson

    Jim Thompson Guest

    Look up how you reader can be configured. In Agent it's like this...

    On %date%, %from% wrote:\n

    which puts the previous poster's information just before the quoted
    material.

    You can easily add your "Hi" if you like... or other cutesy stuff...
    see Spehro's posts for example ;-)

    ...Jim Thompson
     
  15. Joerg

    Joerg Guest

    Hello Jim,

    I'll try to figure it out. But I am using Mozilla which is a Windows app
    without command line stuff and I am more of an assembler kind of guy...
     
  16. Jim Thompson

    Jim Thompson Guest

    Looks like you're getting close ;-)

    All you need is the date attribution and you've got it... see the top
    of this post.

    Why is it that everyone wants to use a single tool to do all
    functions?

    Mozilla/Firefox is a browser, Agent is a newsreader, Eudora is an
    E-mail client, etc.

    ...Jim Thompson
     
  17. Joerg

    Joerg Guest

    It's so much easier. For the same reason I like my new CAD stuff. You
    can scoot back and forth between layout and schematic without ever
    leaving the program.

    Maybe I should try Agent. But every time I switched web SW something
    broke and took hours to fix.
     
  18. Joel Kolstad

    Joel Kolstad Guest

    I've used asitic in school some years back, and for free it's certainly
    decent, although I'd also suggest the OP should check out Ansoft Designer SV
    ("student version") -- it's also free, and can analyze spiral inductors as
    well as performing many other functions that your typical linear RF simulator
    can; it also has a nice GUI (somewhat weird at times, but still easier than
    direct netlist entry) and graphing abilities. One of the examples included is
    a spiral example.

    ---Joel
     
  19. Joel Kolstad

    Joel Kolstad Guest

    I've often wondered how many people actually use (meaning "purchase!") that
    extra option. I suppose that if you're designing a spiral inductor for, e.g.,
    a switch-mode power supply then the actual inductor isn't that critical and
    you could get away with analytical formulas, telling someone to layout a
    spiral of such and such a size and number of turns, but for RF work you
    necessarily end up with a layout as you perform simulations and tweak your
    design anyway, which you'd just import into your PCB tool of choice.

    Have you ever had a real board design where you used that feature, Leon?

    ---Joel
     
  20. Joerg

    Joerg Guest

    Hello Joel,
    It is amazing what kinds of design tools we have these days. In fact, I
    didn't have to pull my old Bronstein/Semendjajew math dictionary off the
    shelf for over a month now. However, when it comes to really intricate
    stuff there is not much progress. When doing wave digital filters I
    still have to resort to DOS tools. Oh well, the same goes for other
    tasks, used grandpa's 70-year old planer to fix something on our deck
    yesterday.

    BTW, did you find other good candidates for the RF engineer opening?
     
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