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AD 8348

Discussion in 'Electronic Design' started by Dario, Nov 20, 2006.

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  1. Dario

    Dario Guest

    Hi to all newsgroup!
    Do someone use this demod developed by Analog Devices?
    I have evaluation board and I read datasheet, but I can't demod direct
    current... I tried many ways, like described in datasheet, but my eval
    board doesn't work correctly at 0 Hz.

    Any suggestion?

    Thanks a lot
    Dario
     
  2. Guest

    Dario--
    What's your application? What analog information are you trying to
    extract? The datasheet states that this is a 50-100 MHz device, which
    doesn't include 0 Hz (DC).

    I haven't ever used Analog Devices demodulators, but I've been
    seriously investigating them for a possibility in a low frequency
    (30-500 kHz) application. According to
    http://www.analog.com/en/subCat/0,2879,770%5F849%5F0%5F%5F0%5F,00.html,
    the AD630 and AD8333 operate from DC to 2 Mhz and DC to 50 MHz,
    respectively.

    I'm not 100% familiar yet with the inner workings of a demodulator, but
    I do know that you have to have an AC signal in order to demodulate it,
    right?

    You also might check into devices like the AD606, AD8304/8307, etc.
    that are demodulating logarithmic amplifiers if you're interested in
    the amplitude only of your signal.

    Good luck!
    -Todd
     
  3. Dario

    Dario Guest

    Dario--
    Thank you Todd for your answer! I'm sorry because my question is not
    very clear...

    I need to demodulate a DVB channel from 800MHz to baseband. I filter I
    and Q baseband signals with a DSP to delete adiacent channels and I
    send it to a decoder. The problem is that baseband channel lacks of
    zero Hz frequency, so SNR is very poor. If I choose a different
    demodulation frequency (to bring DVB channel to higher frequency, about
    from 1MHz to 9 MHz), the SNR ratio is very good.

    So, in the ad8348 datasheet I read that it can demod a signal to DC,
    but I could not realise this... I tried several configurations, but
    Demod doesn't work.

    Maybe a scheme is clearer... I hope to post it soon.
    Thank you for your answer again.
    Dario
     
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