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Analogue FM with high bandwidth modulation signal

Discussion in 'Electronic Design' started by [email protected], Jun 6, 2006.

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  1. Guest

    Hi,
    I am currently involved in a project, part of which is to design an
    analogue FM system which will accept a 20kHz - 200kHz modulating
    signal. This signal will also occur over several orders of magnitude,
    but will be used with a time programmed gain circuit in order to level
    out the modulation input.
    I see most of the posts are related to audio FM, hence much lower
    modulation frequencies, but is there any limitation on the bandwidth of
    the modulation signal for standard FM circuits? Are there off-the-shelf
    ICs which would facilitate this application? If not, what would be
    considered the 'best' design for such a system? The system need not
    transmit more than 10 metres or so, but must be as small as possible -
    so component count is important, and quality may be sacrificed in order
    to maintain a small, light design. This factor is the reason why a
    digital design is not being considered.
    Any suggestions and help much appreciated, this really isn't my area of
    expertise. Apologies for any lack of detail...if more information would
    be useful, please ask.
    Thanks,
    Simon.
     
  2. Rich Grise

    Rich Grise Guest

    Just one question: Is this for school or for pay?

    If you're getting paid for this, I'm sure several of the regulars would be
    happy to offer their consulting services at their standard rate.

    If it's for school, then study your lessons better.

    Just for perspective, a 200 KHz modulation signal on a, say, 100 MHz
    carrier is almost trivial - they've been doing it in broadcast
    transmitters for decades.

    Good Luck!
    Rich
     
  3. Tom Bruhns

    Tom Bruhns Guest

    Sure, why would the ability to modulate stop at 20KHz? As long as the
    carrier is a high enough frequency that you can transmit the sidebands
    you generate with the modulation, and as long as the receiver is also
    designed to receive it, why not? Just look at the circuit you are
    thinking of using (presumably adapted from an audio-range system) and
    see where, if anywhere, there are frequency-limiting components in the
    modulation path. FM audio transmitters commonly apply "pre-emphasis"
    to the audio; you may wish to not do that. A Google search for
    preemphasis will get you to lots of resources.

    Cheers,
    Tom
     
  4. Genome

    Genome Guest

    You might find that you are the victim of a 'SNURK'.

    In this context a 'snurk' is a proposal by persons or people with small
    penises to someone else that causes them to try and implement the subject
    matter of the 'snurk'.

    If suitably directed the 'snurkee' may have the chance to become a troll in
    usenet for the 'snurker'.

    The 'snurker' relies on the fact that they 'know' what they are talking
    about and the 'snurkee' does not but is in a position where they are forced
    to do what they are asked for reasons of a socio-communal-political sort of
    thing.

    The only real solution is to go back and tell the 'snurker' to **** OFF and
    then go down the Arms for a few pints of Heavy with your proper mates.

    Oh, and don't use your personal uni account to post to usenet.

    DNA
     
  5. Mark

    Mark Guest

    FYI Analog satellite TV signals use FM with modulating freq up to 6
    MHz...

    Mark
     
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