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Highest freq oscillators

Discussion in 'Electronic Design' started by Roberto, Oct 14, 2003.

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  1. Roberto

    Roberto Guest

    What are the very highest frequency oscillators out there? I'm guessing that
    it would probably have some exotic component in it, so my other question is:
    what are the highest frequency oscillators out there which use relatively
    "normal" components?

    Thanks in advance,
    Robert
     
  2. The components change gradually and so do the mechanical layouts.
    What is a normal component ? perhaps a BC107 ?
    What is a normal construction ? wirewrap ?

    Rene
     
  3. SioL

    SioL Guest


    http://imagine.gsfc.nasa.gov/Images/introduction/emsurface.gif

    An ordinary light bulb is simplest.

    Next, you could get one of those UV lights, that's even higher.

    If you're talking radio, you should be able to produce a few GHz today
    "easily".

    SioL
     
  4. Perhaps he means what the highest frequency oscillators in fundamental
    mode? The question doesn't make much sense otherwise.
     
  5. There was no mention of a quartz.
    An LC osc can be said to be limited by the semiconductors, as
    you always get a smaller cap, smaller inductor.
    The Q may become a problem when the layout is inappropriate,
    eg 100nH connected to wirewrap.

    Rene
     
  6. Al Yeager

    Al Yeager Guest

    If you consider light waves to be oscillations then UV LEDs would be the winner.

    hth

    al
     
  7. Roberto

    Roberto Guest

    If you consider light waves to be oscillations then UV LEDs would be the
    winner.

    OK, OK, I guess a rephrase is in order... ;)

    I only mean oscillations of current in a wire, not electron clouds in
    mercury atoms! (or something)

    And by "normal" components, I meant thing like semiconductors, crystals,
    etc., as opposed to klystrons [sic] and that kind of thing. I guess it's a
    matter of opinion where you draw the line, though.

    Thanks,
    Robert
     
  8. Active8

    Active8 Guest

    those Klystrons and magnetrons are used because they put out way more
    power than the semiconductor oscillators and they're tuned cavities.

    with semis, you buffer and amplify the output.

    you can start with a 3rd overtone crystal and add freq multipliers up
    into the GHz. alternately, you can use LC oscillators as a start.
    microstrip lines can be used. coaxial resonators are normal enough. you
    can use the parasitic L and C of uhf/microwave transistors to get
    oscillations.

    stripline/microstrip bandpass filters can be modified to make VCOs.
    nothing "abnormal" there.

    in all but the case of a crystal based. coaxial, and maybe stripline
    oscillator, you'll need a pll to stabilize the frequency and even the
    crystal osc may need compensation or PLL stabilization since "stable" is
    a relative term.

    there are gunn diodes used in Gunnplexers. around 10GHz IIRC. i consider
    that "normal" too. those are cool.

    you might try Mini-Circuits, they have some really cool VCOs in the $24-
    $50 range. M/A Comm is one other source.

    otherwise, just build a high freq amplifier. it'll probably oscillate,
    but only if you really want it to be an amplifier :)

    HTH,
    mike
     
  9. John Larkin

    John Larkin Guest

    Commercial semiconductor-based oscillators can be made to work up to
    roughly 60 GHz. It's common to brag about experimental semiconductors
    in terms of their Fmax, max oscillation frequency: I've seen reports
    of 200 GHz or thereabouts.

    I think there are some exotic tubes that oscillate in the millimeter
    region, and FEL lasers are "oscillators" too, I suppose.

    John
     
  10. I only mean oscillations of current in a wire, not electron clouds in
    So the limitation will be I think the wire, not the components... Anywhere
    above 40 to 60GHz you will have great difficulties to find a "wire" that
    will conduct your signal, except on very very short distance. But if you
    accept more exotic transmission medium, like planar waves in a tube, then
    100 to may be 200GHz seems achievable these days. The only problem will be
    to find a device to detect it...

    Robert



     
  11. Phil Hobbs

    Phil Hobbs Guest

    The highest frequencies currently reachable as currents in wires are in
    the blue region of the optical spectrum--about 700 THz or so. You make
    them by exciting surface plasmons in a thin metal film, using a
    metal-insulator-metal tunnel junction. The MIM junction works rather
    like the base-emitter junction of a BJT--it injects electrons which then
    create surface electromagnetic waves on the opposite surface of the
    film, rather than drifting through the depletion region to the collector
    contact.

    The spectrum is set by the forbidden gap of the tunnel barrier--lower
    gaps lead to longer wavelengths. Since these are extremely cheap and
    can be modulated very rapidly (terahertz), they may be attractive as
    light sources in short range optical communications. The drawbacks are
    their very broad emission spectrum, typically 100 nanometres (about a
    25% fractional bandwidth), which leads to lots of problems with
    dispersion, and their very low efficiency at present.

    My work at present is in miniaturizing classical microwave technology
    (to 0.1 to 0.25 um sizes), with similar MIM tunnel junctions as active
    devices, for use in optical interconnections in servers and routers.
    This also involves electric currents in (very small) wires, in the 200
    THz (1.5 micron) range.

    Cheers,

    Phil Hobbs
     
  12. Leon Heller

    Leon Heller Guest

    How about the oscillators in satellite receivers - must be about 10 GHz
    or so. Millions of these are in use.

    Leon
     
  13. Tim Shoppa

    Tim Shoppa Guest

    Assuming "normal" means parts connected by real conducting wires, the
    speed of light sets the scale. For a size of a few cm the number you
    get is 10GHz or so.

    Abandon wires and you're in TWT (traveling wave tube) territory (klystrons,
    magnetrons, etc.).

    Tim.
     
  14. Roberto

    Roberto Guest

    Assuming "normal" means parts connected by real conducting wires, the
    And I guess you can't exactly use TWT for communications? Or can you? :-S

    Thnaks,
    Robert
     
  15. maxfoo

    maxfoo Guest

  16. A Laser, with the shortest wavelength. What's that? UV? Blue?


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  17. But the light is not a pure frequency, it is not monochromatic like a
    laser is. A regular blue or UV LED has a purer, less polychromatic
    output than a light bulb, but a laser is truely monochromatic.


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  18. A UV Laser is more monochromatic than a UV LED.


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  19. The next time you walk thru an automatic door, look up at that small
    box above it, which has a microwave oscillator in it. This is usually
    a Gunn diode or IMPATT diode in a cavity. It might oscillate in the X
    band.

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  20. The reflex klystrons that are the size of the tubes in a tube radio
    put out well under 1 watt. See http://www.tubecollector.org/707b.htm
    Not necessarily. Here's a publiation that talks about a Gunn diode
    that puts out 45 GHz.
    http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1980ITMTT..28.1460M

    Here's a 120 GHz HEMT oscillator. Now, that's prtty high freq. If
    you go much higher than that, you are in the low end of the infrared
    band.

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