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[Q] pulse generaton with a carrier

Discussion in 'Electronic Basics' started by googler, Sep 13, 2005.

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  1. googler

    googler Guest

    I am trying to find a way to generate a <10ns electrical pulse with
    400MHz carrier inside the pulse at 0.1~1MHz repetition rate.

    I was trying to combine a <10ns electrical pulse and a 400MHz carrier
    with a frequency mixer. But between <10ns electrical pulse there is the
    leakage of 400MHz with a small amplitude. So far pulse train looks fine
    but I'd like to have a better pulse shape.
  2. Don Bowey

    Don Bowey Guest

    What are you using for the modulator (multiplier)? A double-balanced
    modulator should suppress the carrier 40 to 60 dB between the 10ns bursts,
    and will probably improve the 400MHz waveform.

  3. googler

    googler Guest

    I was using a frequency mixer from Minicircuits. Its model number is

    LO/RF input freq. : 0.1-500MHz
    IF input freq. : DC-500MHz

    If possible, would you please recommend any company that sells the
    double balanced modulator ?
  4. Don Bowey

    Don Bowey Guest

    Before you try a different mixer, it would be a good idea to check the
    voltage ratio of the 400 MHz RF input to the 10 nS pulse, which I'm guessing
    you are applying to the IF port. Since the pulse is the "LO signal" it
    should be about ten times the amplitude of the 400 MHz signal. If
    correction is not needed or does not improve the output signal, then another
    mixer will help.

    The ZX05 family of double balanced mixers looks good. Be sure to choose by
    first matching the required LO signal to your pulse generator capability.

    Realize that I'm shooting in the dark because I don't know the specifics of
    your equipment, so second-guess me and ask any questions you may have.

  5. Jasen Betts

    Jasen Betts Guest

    in that 10ns you'll get 4 cycles of your 400mhz carrier

    could you just use a 400Mhz source, divide it by 8 to get a 100mhz source
    (with 10ns wide pulses) and divide that by 500 (or 512) to get your ~100Khz

    | ____ |
    clk1 | | | |
    --------+-(divide by 8)--+--(divide by 500)-+-|D _| +-|~~\ out
    400Mhz | | | Q|------| & )---
    | +----(inveerter)-----|clk | +-|__/
    | |____| | 3-input and gate
    | D-type flip-flop |

    if you want to sontroll the burst rate you'll need a programable divide
    stage instead of a fixed divide by 500 - what you put there depends on what
    form your control takes.

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