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Engineers Discover How To Make Antennas For Wireless Communication 100x Smaller Than Their Current Size (sciencemag.org)
Engineers have figured out how to make antennas for wireless communication 100 times smaller than their current size, an advance that could lead to tiny brain implants, micro-medical devices, or phones you can wear on your finger. Science Magazine reports: The new mini-antennas play off the difference between electromagnetic (EM) waves, such as light and radio waves, and acoustic waves, such as sound and inaudible vibrations. EM waves are fluctuations in an electromagnetic field, and they travel at light speed -- an astounding 300,000,000 meters per second. Acoustic waves are the jiggling of matter, and they travel at the much slower speed of sound -- in a solid, typically a few thousand meters per second. So, at any given frequency, an EM wave has a much longer wavelength than an acoustic wave. Antennas receive information by resonating with EM waves, which they convert into electrical voltage. For such resonance to occur, a traditional antenna's length must roughly match the wavelength of the EM wave it receives, meaning that the antenna must be relatively big. However, like a guitar string, an antenna can also resonate with acoustic waves. The new antennas take advantage of this fact. They will pick up EM waves of a given frequency if its size matches the wavelength of the much shorter acoustic waves of the same frequency. That means that that for any given signal frequency, the antennas can be much smaller. The trick is, of course, to quickly turn the incoming EM waves into acoustic waves.
The team created two kinds of acoustic antennas. One has a circular membrane, which works for frequencies in the gigahertz range, including those for WiFi. The other has a rectangular membrane, suitable for megahertz frequencies used for TV and radio. Each is less than a millimeter across, and both can be manufactured together on a single chip. When researchers tested one of the antennas in a specially insulated room, they found that compared to a conventional ring antenna of the same size, it sent and received 2.5 gigahertz signals about 100,000 times more efficiently, they report in Nature Communications.
The team created two kinds of acoustic antennas. One has a circular membrane, which works for frequencies in the gigahertz range, including those for WiFi. The other has a rectangular membrane, suitable for megahertz frequencies used for TV and radio. Each is less than a millimeter across, and both can be manufactured together on a single chip. When researchers tested one of the antennas in a specially insulated room, they found that compared to a conventional ring antenna of the same size, it sent and received 2.5 gigahertz signals about 100,000 times more efficiently, they report in Nature Communications.
There was a similar antenna developed a few years ago that used a very thin metal membrane who movement was excited by HF magnetic field. Then bounce a laser off for the detection. It did not have a lot of gain, but had near zero noise (just quantum fluctuations) so was very good for receiving.
Chu's limit appears to have been somewhat pragmatic in assuming that certain kinds of electrical circuits could not be feasibly realized.
Chu's Limit—a limit no more — 23 February 2017
The part I understand: built and measured.
Whoever did the write up is 180* out.. EM is the shorter wave ( hence the terms shortwave and microwave radio) and audio are the shorter waves .. but interesting concept
Audio is the Longer wave (more physical distance between peaks)
Avoid the term "audio"; 60 MHz acoustic waves (as described in this paper) are not audible.
Sound (in any normal medium) is far slower than light, so sound waves at some frequency are much shorter than radio waves of the same frequency. They're describing antenna that oscillate acoustically at millions of hertz; the same frequency as the EM waves being received, not thousands of hertz as in audible sound.
Maw! Fire up the karma burner!
Or your reading comprehension is simply rubbish. They're using EM vs acoustic of the same frequency, that's kind of the point.
And, since EM has the higher speed, it also has higher wavelength at a given frequency.
No, they did it in order to measure the efficiency precisely, which requires shielding from both outside interference and internal reflections.
The f-117 in question flew over the exact same mountain for three nights on it's route in. It had only one flying route in and out of serbia.
Anything can be done able if you wait for a good shot and only turn on your radar at the last second so they don't have time to evade.
Why does everyone always forget that part? The bombers had one mountain they were required to fly over as it was the only clear zone in from the neighboring countries who restricted what could fly where.
That brought down the plane as much as long wave radar
i thought once I was found, but it was only a dream.
Ok, I get that. But I don't get how the EM waves make it vibrate in the first place and surely if the antenna is normally far too small to intercept the waves of a given frequency they'll just pass it by and nothing happens?
Construction involves piezoelectric material, which changes shape according to the strength of electric field in which it is placed. It means that if you apply varying field, it will follow field changes with own shape change. The opposite holds true too: if you mechanically change the shape of an object having piezoelectric property, it will generate electric field.
The antenna doesn't need to be placed across the whole wave, it just needs to resonate with the rhythm of the change: when it contracts because of the mechanical (acoustic) ringing, it has to also be pushed by external field to do so; when it expands, the external field has to pull it too - just like when you are pushing someone on a swing.