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Science Technology

Old Marconi Patent Inspires Tiny New Gigahertz Antenna 76

Posted by samzenpus from the getting-small dept.
agent elevator writes Gehan Amaratunga and a group of engineers in England noted that the Guglielmo Marconi's famous British patent application from 1900 had an interesting and little noticed detail. It depicted a transmitter linked to an antenna connected to a coil, which had one end dangling while the RF signal was fed to the middle of the coil. That detail inspired them to develop a way to reduce the size of a GHz antenna without significant transmission loss by using dielectrics as the radio wave emitting material instead of conductors.
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Old Marconi Patent Inspires Tiny New Gigahertz Antenna More

Old Marconi Patent Inspires Tiny New Gigahertz Antenna

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  • My B.S. Detector is Going Off (Score:5, Informative)

    by Bruce Perens ( 3872 ) <bruce@perens.com> on Monday April 20, 2015 @02:01PM (#49513269) Homepage Journal

    Marconi's connection to the center tap of a coil with one end not connected worked by broken symmetry? Really? It wasn't just a method of tuning a coil to the correct reactance for a particular frequency?

    • I agree: it looks like a diagram denoting a tune-able antenna.

      • It looks like a ham radio "screwdriver" antenna except miniaturized by a 3-4 orders of magnitude to match the 3-4 orders of magnitude change in wavelength.

    • Re: (Score:1)

      by Anonymous Coward

      Clearly you missed the bit where they invoked quantum mechanics, surely that explains away all the inaccuracies, like the fact you can already buy chip scale dielectric antennas

      • Clearly you missed the bit where they invoked quantum mechanics, surely that explains away all the inaccuracies, like the fact you can already buy chip scale dielectric antennas

        The thing that I really hate about Innovation Stories is that the reporter invariably doesn't understand what's going on, and invariably is easily convinced that The Obviiously Very Technical People have some very valuable invention.

    • Re: (Score:3)

      by JonWan ( 456212 )

      Clearly none of the "Engineers" had a ham license.

      • Exactly. That's a multiband antenna system. Change bands, change the tap point. The point they're missing is grounding of the "asymmetric" half of the antenna, and that's to keep a static charge from building in the antenna that'll zap through your electronics (or you) for safety reasons. The center tapped grounded coil feedpoint matching is also less noisy than an inline tuning coil.

        • The point they're missing is grounding of the "asymmetric" half of the antenna, and that's to keep a static charge from building in the antenna that'll zap through your electronics (or you) for safety reasons.

          Sometimes. But you're missing what a Counterpoise [wikipedia.org] does.

          • That is a good point, but I'm not sure how well it would work over standard fractional wavelength radials on larger systems. The Marconi drawing has lighting and static charge protection from the grounded side of the voltage transformer that's being fed from the transmitter. It could be very useful for space conscious form factors, and I don't know anyone that wants a radial and whip system for a cell phone.

            From Marconi's drawing, it looks more like use of a coil as either a resonant stub or shorted stub [wikipedia.org]

    • I was also a bit surprised by that part. It rather looks like a wave is launched into a piece of dielectric, which then may act like a dielectric waveguide. Somewhat. More or less...
      In any case I can hardly believe that quantum theory is needed to explain the behaviour of antennas. Most surprising, however is to find such clumsy explanation in Spectrum, the flagship journal of the IEEE.

      • Re: (Score:1)

        by Anonymous Coward

        I've read the underlying papers: they do not use quantum theory to explain the behavior of antennas.

        "Marconi's connection to the center tap of a coil with one end not connected worked by broken symmetry? Really? It wasn't just a method of tuning a coil to the correct reactance for a particular frequency?"

        Well, of course one purpose was to have a variable inductance, but that's not what's at question.The issue here is why the other end of the coil is not earthed, apparently intentionally.

        The issue about the

        • If the end of the coil that is hanging is grounded (earthed), it becomes an autotransformer. As it's shown, it's a variable inductor and the disconnected end is irrelevant and has no meaningful physical effect at the frequency a spark transmitter could have reached.

          This comment [slashdot.org] seems to get closer to what they actually mean in their scientific paper. But the article about it is garble and the paper might suffer from second-language issues, and a lack of familiarity with the terms used in RF engineering.

          • Re: (Score:2)

            by storkus ( 179708 )

            ...lack of familiarity with the terms used in RF engineering.

            Got beaten to the punch here. I was about to submit this confusing quote from TFA:

            the two-wire ribbons used during televisionâ(TM)s first few decades to send RF signals from rooftop VHF antennas to television sets without any loss. The electric RF current in the two conductors flow in opposite directions and have opposite phase. Because of the translational symmetry (the two conductors are parallel) the radiation fields cancel each other out, so there is no net radiation into space.

            Took a few reads before I finally figured out they were referring to 300-ohm twin lead...

            [digression]Captcha for this is "shudders". Indeed...[/digression]

            • Yep. A physicist trying to explain a balanced line to other physicists, without knowing the word for it.

              Haldane would be spinning in his grave.

      • IEEE is a rotten paywall and should be abolished.

    • Yes, Marconi simply provided for varying the inductance. At low frequencies some floating turns have little effect. The coil is physically short in terms of wavelength and there isn't enough stray capacitance to get much resonant or non-resonant current flow through the floating leg.

      In some cases people actually short out turns they don't want. That's seen mostly with silver-plated coils in transmitters, where resistance losses associated with the resulting circulating current are sufficiently low. The

    • Plus, did you look at their paper....? Link: http://journals.aps.org/prl/pd... [aps.org] I've never seen a more phallic figure (Figure 1c.) in an E&M paper in my life. Some serious editor trolling going on with this paper.

  • 100 year old news? (Score:3)

    by gurps_npc ( 621217 ) on Monday April 20, 2015 @02:04PM (#49513305) Homepage
    So basically, this is a 100 year old invention, that some people just happened to notice today?

    Hey, people I don't know know if you are aware, but if you take a radar unit, drop the receiver and turn up the power, you can cook FOOD on it to!

    • No, basically, this was INSPIRED by a 100 year old invention. Not quite the same thing.
      • Correct... it wouldn't be wise to point to "prior art" now would it? But inspiration is perfectly fine... really patent officer, that's all it was! Inspiration!

    • Re: (Score:3)

      by cdrudge ( 68377 )

      Hey, people I don't know know if you are aware, but if you take a radar unit, drop the receiver and turn up the power, you can cook FOOD on it to!

      Really? That's really cool. I guess it's a RadaRange then?

    • Excuse me but that sounds entirely implausible. Cooking food with a radar unit? I'll believe it when someone uses one to, say, melt a chocolate bar. Until then keep your loony theories to yourself!

      • Excuse me but that sounds entirely implausible. Cooking food with a radar unit? I'll believe it when someone uses one to, say, melt a chocolate bar. Until then keep your loony theories to yourself!

        Oh, it's quite possible... an APG-66 radar kit [wikipedia.org] (usually parked inside the radome of an F-16 jet fighter) can cook a hot dog placed 2' in front of the pitot tube in very short order once you flip it into active mode. That's why they usually point the jet's nose out somewhere big and empty when they test it, and then make damned sure no one walks within 150' of the jet's front during testing.

        (hint: both the typical radar unit and microwave oven share one core component in common - a magnetron.)

  • Obviously (Score:5, Funny)

    by Anonymous Coward on Monday April 20, 2015 @02:05PM (#49513315)

    This means that Guglielmo Marconi's hard work was stolen without compensation and he has no incentive to invent anymore. Extends patents to 115 years!

  • That sure looks darn similar to the schematic for a variable inductor. You often use inductors to balance the feed on an antenna system (usually paired with capacitors) and would seem to make sense. Otherwise why the arrow in the diagram?

  • I read that as Macaroni patent (Score:1, Interesting)

    by Anonymous Coward

    I was intrigued. But no, Marconi... that... that makes more sense.

  • have to admit... (Score:4, Interesting)

    by hitmark ( 640295 ) on Monday April 20, 2015 @02:21PM (#49513451) Journal

    I read the title as "old macaroni patent" on first glance.

    • Re: (Score:3, Funny)

      by rubycodez ( 864176 )

      And it's so ambiguous. Is that a patent on old pasta? a macaroni patent that expired? A patent inscribed on a tube of pasta? patent on fancy 18th century duds?

  • Maxwell's equations fail? (Score:3)

    by wbean ( 222522 ) on Monday April 20, 2015 @03:39PM (#49514127)
    Tech reporters should be licensed. I seriously doubt that Maxwell's equations are failing: "Maxwell’s equations explain how high-frequency flows of electrons in conductors generate electromagnetic waves, but they do not explain how an insulating material, where there is no flow of electrons, would also act as an antenna."

    • It's especially sad to see this from an IEEE publication (even spectrum).

      First, the major unifying concept in Maxwell's equation was the displacement current, a quantity for the changing field in a dielectric with units as current density. This answers the age-old question, "how do you have a current circuit when one part (a capacitor) is clearly 'broken' and not conducting?" Maxwell was the first to answer the question with a solid theory. So a better way to write the sentence you quote would be, "Maxwell

    • Re: (Score:2)

      by Kim0 ( 106623 )

      "Lens" is the common name for an antenna made of insulating material.

  • The patent detail has nothing to do with the subject. It's a variable coil that's depicted, signalized by the arrow cursor ( like a potentiometer, but a coil)
    The article is marketing wank.

  • Didn't Marconi steal the notebook of Jagdish Chandra Bose and came up with the idea of the "coherer"? So wonder where he pinched this idea from.

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