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Temperature effect on 2.4GHz RF

Discussion in 'Electronic Design' started by Boki, May 29, 2007.

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  1. Boki

    Boki Guest

    Hi All,

    When 2.4GHz short range module boots up, senses the temperature,
    adjusts the RF parameters itself.

    What's the effect by temperature ?

    Best regards,
    Boki.
     
  2. Jim Yanik

    Jim Yanik Guest

    temp changes will alter tuned elements that determine the oscillating
    frequency. semiconductor junctions change with temp,capacitance changes.
     
  3. Boki

    Boki Guest

    Ya, I believe it.

    However, I think the effect should very small, or should be de-effect
    by other components.

    It seems our module try to adjust digital algorithm to fit the
    changes.

    However, I can't make sure that.

    Boki.
     
  4. Chris Jones

    Chris Jones Guest

    The carrier frequency will normally be generated with a PLL so it will be
    locked to a crystal. Since it has a crystal oscillator, it will probably
    re-tune itself using the crystal as the reference frequency to adjust the
    L-C circuits. These things have to be made so that they will work with
    maybe 20% manufacturing tolerance on the capacitors so the automatic
    adjustment facility is already needed anyway in many cases. The inductance
    value of the on-chip inductors is defined by lithography so it is very
    accurate and stable but the capacitor tolerance is set by the thickness of
    deposited layers and hence the wide tolerance. The series resistance of
    the inductors (and hence the Q) is quite temperature dependent, like the
    resistivity of most metals. They might calibrate this out as well.

    Chris
     
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