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Your very own high-speed pattern generator

Discussion in 'Electronic Design' started by Winfield Hill, Feb 10, 2008.

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  1. Can't afford a new Agilent series 81141A high-speed
    pattern generator, at only $101,673 starting price?
    My local rep writes to say that a refurbished N4901B,
    the older model capable of 13.5GB/s, costs $32k, or
    $54k for full BERT (not JBERT?), but only if ordered
    by Feb 28th. Call ASAP to reserve a unit, he says.
     
  2. John Larkin

    John Larkin Guest

    What sort of speed, patterns, and levels do you need?

    The newish SRS clock box with the PRBS option ain't bad for $3K new.
    We just got one, and it's interesting. It's a 2 GHz box, but they
    limited the prbs to 1.55 GHz, presumably because the EclipsPlus shift
    register dies somewhere below 2G. The layout is cute, seven SO-8
    flipflops in a circle with an xor gate off to the side, like a frying
    pan with a handle. It would go faster if they did the xor some other
    way.

    I've got it running over the weekend into an infinite-persistance
    sampling scope to see if there are any outliers in the eye diagram.

    I wonder if there's a market for a small pattern generator. It
    shouldn't be really hard up to, say, 5 GHz.

    John
     
  3. EE123

    EE123 Guest

    What is JBERT?
     
  4. Fred Bartoli

    Fred Bartoli Guest

    EE123 a écrit :

    Being what J stands for for TI packages it's DILBERT.
     
  5. Hal Murray

    Hal Murray Guest

    Some FPGAs come with high speed serial ports and an option
    to bypass the 8b/10b or 64b/66b encoders. If your pattern
    fits in the on chip ROMs, it should be straightforward to
    emit an arbitrary pattern at 10 G bits/sec. (I haven't done
    it, but it sounds like fun.)
     
  6. Design your own SiGe chip ? Unfortunately the
    chip fabs that do custom chips stick to CMOS.
    Configurable CMOS that is. If you had to pay
    for the photo masks yourself, one for each
    layer, you'd spend a fortune just on them.

    Rene
     
  7. John Larkin

    John Larkin Guest

    No, just use a fast FPGA to make patterns at 400 MHz or so, and mux up
    its outputs with some fast ECL, all stock parts. As someone noted,
    many of the high-end fpga's already do gigabit serial streams, but I
    don't know if they are general enough to be used directly as a pattern
    generator.

    Yesterday we were, independently, brainstorming a box that would
    accept a customer trigger and generate some number of arbitrary
    digital and analog outputs, with picosecond jitter and resolution on
    all the output edges. We might do it if things slow down a little. We
    occasionally get an inquiry for stuff like this.

    John
     
  8. Phil Hobbs

    Phil Hobbs Guest

    I'd certainly like a 2**32-1 prbs generator that would go at least 5
    Gb/s and would drive a telecom modulator (+24 dBm). Faster would be
    better, but 5 Gb/s would definitely be worth buying if it were under,
    say, $20k.

    Cheers,

    Phil Hobbs


    PS: Now who would have suspected that Winfield Hill would stoop to FS
    spamming SED? ;)
     
  9. John Larkin

    John Larkin Guest

    That's do-able. Some GigaComm logic plus moderate dirty tricks could
    make the sequence, and then a couple of the Hittite 20 GHz distributed
    amps to drive your e-o modulator to 5-6 volts p-p. $1500 worth of
    parts maybe.

    Shocked, shocked.

    John
     
  10. Winfield

    Winfield Guest

    I was trying to make a joke - tongue in cheek,
    hey, who who can afford $32 or 54k for a pulse
    generator, let alone $101k? Sheesh! The email
    I received from Agilent's rep was unsolicited,
    and filled with excitement for this special deal
    we'd jump at, but would disappear by the 28th.
     
  11. MooseFET

    MooseFET Guest

    Here's an idea I should save for a patent or perhaps it is too loony
    for even that:

    There are materials with non-linear optical properties that could be
    used to cause a laser beam to deflect back and forth at a rate near
    the GHz range. Rubidium vapor in the one I am thinking about right
    now but there are some doped crystals that also would do this.

    Two such devices at right angles could direct a Laser beam in a
    circle. This circle would strike a light switching device such as an
    LCD with a great many segments in a ring.

    A bit of non-imaging optics could bring the light down to one location
    or put it onto a fiber. A lot of light would be lots in the process
    so the Laser will have to be modestly powerful.

    At this point, if enough segments are in the light switch, you can
    have light that is switching at a great many GHz.
     
  12. Phil Hobbs

    Phil Hobbs Guest

    I've recently bought a couple of 40 Gb/s modulators (30 GHz 3 dB BW)
    from Avanex for about $6k each. That's about as fast as I need to go
    for the foreseeable future. They're about 70% efficient optically, but
    need about +24 dBm worth of drive.

    Cheers,

    Phil Hobbs
     
  13. Phil Hobbs

    Phil Hobbs Guest

    Me too. Agilent FS spam was too funny to miss.

    Cheers,

    Phil Hobbs
     

  14. This is why high tech companies should never hire people who've sold
    used cars. :(


    --
    Service to my country? Been there, Done that, and I've got my DD214 to
    prove it.
    Member of DAV #85.

    Michael A. Terrell
    Central Florida
     
  15. Winfield

    Winfield Guest

    At what frequency?
     
  16. krw

    krw Guest

    Why? Because they'd be too embarrassed to take the job?
     
  17. Phil Hobbs

    Phil Hobbs Guest

    They're only about 1 dB down at 20 GHz, iirc. At that sort of speed,
    the phase nonlinearity is at least as important as the rolloff.

    Cheers,

    Phil Hobbs
     
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