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Where is RF Ground?

Discussion in 'Electronic Design' started by Xanax, Nov 1, 2003.

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  1. Xanax

    Xanax Guest

    Hi all,
    I'm a bit miffed about where RF ground is.
    Can I assume it's just the Gnd Zero Volt Line?

    Where can I get info on home prototyping of RF circuits using groud planes
    and anything that reduces RFI.

    Cheers,
    Xanax.
     
  2. mike

    mike Guest

    RF ground is exactly where you define it to be.
    It's a single point in space, usually on/in a conductor.
    Every place else is NOT RF ground. You cannot have
    RF ground in two places at once.
    mike

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  3. Definitely not. Any piece of conductor has resistance *and inductance*,
    so between any two points on your 'Gnd Zero Volt Line' there is a finite
    impedance.

    You have to *decide* where your 'r.f. ground' should be, and allow for
    the inevitable impedance if you 'ground' something at any other point.
    The ARRL and RSGB publications are good sources. Google!
     

  4. In analog electronics, the GND can be defined everywhere, usually
    where the powersupply is connected to the pcb. Then the GND is
    propagated to the subcircuits by tracks of their own.

    This doesn't work this way with RF.
    The RF GND is usually the metal case around your pcb.
    Then you tend to have a GND plane on your pcb, being
    connected to the case wherever possible along the circumference
    of the pcb. Depending on the frequency range of the active
    components, not necessarily the intended use, you have to
    take care that no lambda/4 or lambda/2 antenna can form.

    That means when working with 2GHz amplifiers, structures
    longer than 2.5cm (1") are critical. It doesn't matter
    whether the intended use is only 100MHz.

    Rene
     
  5. R.Legg

    R.Legg Guest



    Misquoting Father Guido Sarduchi, "Ground is everywhere".

    That is for the faithfull.

    In practice, it's never where you want it to be, but a low
    conductivity ground plane at a known distance helps.

    One mother of a reference, but not specifically oriented to RF would
    be Betz's "Switching Electronics"

    http://murray.newcastle.edu.au/users/staff/reb/#Elec323-switching-electronics

    At 3Meg, it's worth the trouble to download.

    RL
     
  6. Xanax

    Xanax Guest

    Thanks Rene!
    That't the clearest explaination of an RF GND I have got.
    Cheers,
    Xanax.
     
  7. Xanax

    Xanax Guest

    Thanks RL,
    That URL came in very handy.
    It's nice of the lecturer to put his notes on-line I know plenty of narrow
    minded lecturers who would think their jobs would be at rick by publishing
    their notes.
    Cheers,
    Xanax.
     
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