New high speed Sony CMOS sensor announced today

Discussion in 'Professional Video Production' started by Smarty, Feb 19, 2007.

  1. Smarty

    Smarty Guest

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  2. Martin Heffels, Feb 19, 2007
    #2
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  3. Smarty

    Smarty Guest

    Well Martin, I will have to assume you are joking. Even though 432 MHz does
    lie within the UHF spectrum which (we) hams utilize, the amount of radiated
    EMI coming from a Sony sensor being strobed at this frequency would be way
    below the atmospheric / Boltzman noise a very short distance from the
    camera.

    Smarty
     
    Smarty, Feb 19, 2007
    #3
  4. I was joking of course :) We have to assume that Sony will provide proper
    shielding as well, to reduce the RFi output of the camera. But obviously it
    would only be a concern at a contest when you try and shoot some stuff
    around 4 stacked 30 element 70cm yagi's with 25dB pre-amp. Something like
    that :))

    -m-
     
    Martin Heffels, Feb 19, 2007
    #4
  5. Smarty

    Smarty Guest

    Martin,

    I became a true believer in the magic of proper shielding after using a
    remarkably sensitive HF receiver built on a PCI card, stuffed into a Dell
    low-budget desktop machine. See:
    http://www.shortwavestore.com/sws/product.php?productid=582&cat=0&page=1

    How you can hear weak microvolt signals when this board is sitting in
    switched 5 and 12 volt bus noise from DC to nearly a GHz (800 MHz bus)
    defies belief IMHO. But yet it works and works well.

    Stacked 30 element yagis and 25 dB preamp would hear all sorts of stuff, but
    then again, the front to back ratio / beamwidth of the array as well as the
    elevation beamwidth would give you tens of dB of spatial rejection.

    Smarty
     
    Smarty, Feb 19, 2007
    #5
  6. Yeah, the software radios are quite nice. It's amazing how they can keep
    out the RF generated by the computer, while some of them are crammed inside
    the computer :)
    :)

    -m-
     
    Martin Heffels, Feb 19, 2007
    #6
  7. At first glance it's true, but then you think a bit about the way
    those cheap boxes are designed (at least at Dell, I work there!) -- to
    minimize the shielding (cost) you do a lot to balance the radiation.

    In a previous life (before VLSI was bought by Philips) I worked on a
    project to eliminate most of the shielding requirements entirely --
    just make sure that every signal was balanced with one very nearby. It
    works really well at GHz frequencies and it saved on wires as well.
    You just run 20 wires from here to there (< 1/2 inch of board width
    even with a 4 layer board) and make sure that any H/L transition is
    balanced with a L/H transition, make sure there are enough to power an
    A/C to D/C converter in the second chip and you wind up with no power
    plane (or power plane radiation) and no signal RFI. And very little
    conducted EMI.

    At a couple of inches you could do decent RF without much (or any)
    shielding. Of course, computers are getting smaller every year, so it
    might be a bit more challenging now to find any spot 2 inches from the
    CPU and memory.....

    --Charles
     
    Charles Marslett, Feb 24, 2007
    #7
  8. Smarty

    Smarty Guest

    Charles,

    This is a really surprising and clever design technique, and one which I
    never knew existed. The benefit will degrade from any lack of symmetry in
    rise times and fall times such as to not exactly cancel one-another, but
    apparently this is not an issue in the Dell designs. Also, the approach
    works well in the digital domain, but it would be unavailable as a design
    option when doing mixed or analog-only PCB or backplane layout.

    As another hardware designer, you will probably appreciate the single most
    impressive piece of analog shielding I have personally ever seen,. which was
    in a fairly recent ICOM wide band receiver I purchased which continuously
    tunes from VLF to microwave frequencies. You can literally tune the receiver
    to any of the frequencies where the internal local oscillators of the radio
    reside / operate including the BFO, and 3 IF/mixer stages, and not hear even
    a faint hint of these signals even though they are being generated a few
    inches away from a super-sensitive FET front-end with .1 microvolt
    sensitivity. In this case, the shields were literally double copper Faraday
    cages, soldered along their entire seams and to the ground plane of the PCB.
    The isolation was at least 100 dB, probably more.

    This is off-topic for this newsgroup, so I will end it here.

    Smarty
     
    Smarty, Feb 25, 2007
    #8
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