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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.
Does it break the Chu Harrington limit? How is the noise performance given it's a piezo material?
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.
Over-The-Air television
Wait! What? Is that legal? I'm going to ask my gender transition counselor about that. I don't believe people really broadcast valuable content around... no way bro.
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.
If the wavelength is large enough, it becomes basically impossible to hide an aircraft with stealth shaping. So things like VHF radar will typically pick up stealth aircraft. So far the main issue has been that large wavelength antennas take up too much space precisely because of the limits explained in the article. If this stops being the case then VHF radars can be physically much smaller and portable and render stealth useless.
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!
Part of shaping is that the reflected energy is AWAY from the transmitter. So you may see stealth designs that channel and eject in an upward manner where only aerial detectors may pick it up. There's also absorption. There could even be delays instead of hiding so that it may appear the target is further away from the receiver than it actually is.
For those of you who read about that absolutely crazy idea to send chip-scale (or chip "mass", they may be very thin objects like a film) interstellar probes riding on gigawatt beams of laser light (that would accelerate them to .2C in a few hours!), "maybe" this helps solve a problem.
How do they communicate with Earth?
This might allow them to RECEIVE (over interstellar distances?) a very powerful signal even if they are very tiny. The only problem is, I don't see how they could SEND back data; in addition to antenna size don't you need power? (My knowledge of physics is woefully inadequate to evaluate this). Short of them carrying self-replicating nanobots that could construct a large antenna at the destination using local materials (and local power), I don't see how even having a good antenna would allow them to get a signal over trillions of kilometers with even an enormous (space-based) receiving antenna. Does anyone know how the Starshot project intended on sending a signal back?
On the other, for LOCAL communications (say for chip sized probes scattered over a wide area), this might be a key breakthrough. Imagine a carrier spacecraft with a powerful communications subsystem settling into orbit around say Titan. It spews hundreds (thousands?) of these little chips which, with a little protection/good surface/weight ratio might be able to gently break into Titan's thick atmosphere. Then, once on the "ground" (or floating in the Titan seas) they could communicate back to the orbiter which would then relay the observations back to Earth. (How to keep them powered in the low light/liquid nitrogen temperatures is an exercise left to the reader).
Or this could be great for surveillance (or spying) or wildlife cameras (or spying) or ingestible sensors/cameras (or spying)
Antennas in my fillings are receiving Ronald Reagan speeches about host files.
APPS!
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 more ... having a lightening attractor on the roof.
Not only does a white roof look better, it actively prevents global warming, as it reflects more sunlight back into space. If anything we need to lighten more of them!
No, they did it in order to measure the efficiency precisely, which requires shielding from both outside interference and internal reflections.
There was an urban legend that a man with a drill bit or titanium implant was able to hear BBC Radio 1 whenever he drove near a large national radio transmitter.
Vintage computer adverts: http://www.vintageadbrowser.com/computers-and-software-ads
Correct. Improvements to batteries happen constantly but never make it to the people. To the people.
(STORED) POWER TO THE PEOPLE!!!
Wanna buy a shirt?
https://www.redbubble.com/people/stealthfinger/shop?asc=u
So, next to feeling the EM waves of my WiFi router i will soon also be able to hear them.
I wonder what "they" will tell me to do....
Why are other peoples sig's always more witty ???
The antenna is 2 stage - it picks up the EM waves which essentially get converted into vibrations of the same frequency which are then converted in electircal signals. 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?
I'm obviously missing something here but RTFA article doesn't help and the nature document is a bit over my head. Can anyone explain whats going on in laymans terms?
Yes, you have. The conversion you mean is probably an audio signal modulated on a (much) higher fixed (unless modulation is FM) frequency EM signal. In that case, you receive the EM signal, separate the effects of the modulation by subtracting (filter, mix, whatever) the fixed EM signal and go on to recreate the audio according to the modulation used.
In this case, you convert an EM signal directly in its same frequency 'sound' equivalent. Because 'sound' (or pressure) waves travel slower (~340 m/s in average sea-level pressure air) than EM (a bit less than 3000000 m/s in vacuum, light is a special kind of EM) waves, you need less 'distance' in the materials that need to resonate with the frequency. The signal energy is now stored as stresses between molecules inside the material instead of electrons bumping/traveling through the material. Do note the speeds of 'sound' and 'light' are quite a bit different in various materials, but most of the time 'light' is a LOT faster than 'sound' and thus travels a MUCH longer 'distance'.
The novelty here is two-fold. 1) They found a way to directly convert EM waves into their 'sound' equivalent. 2) They developed/found an appropriate material that can 'detect' (turn into an electric signal) the stresses of 'sound' waves at very high frequencies.
Here is a part of the article:
During the receiving process, the magnetic layer of ME antennas senses H-components of EM waves, which induces a oscillating strain and a piezoelectric voltage output at the electromechanical resonance frequency.
In other words, the material uses magnetic detection (also done by coils, like in AM ~1MHz / 300 meter radios... which are a lot smaller than a 300 meter wire antenna equivalent) and because of its shape it starts to oscillate with the signal. Not electromagnetically, like in almost every other EM wave antenna, but mechanically. It creates stresses in the material (oscillating strain). They convert that strain back to an electric signal, using piezoelectric properties of the material (like the quartz in a 'push button' style lighter which emits a(n electric) spark that ignites gas). Oscillation only happens when the 'distance' in the material very closely matches the frequency of the receiving/transmitting wave; in this case in its 'sound' form. This is why you need to tune a guitar to get the right tone and 'normal' EM antennas need to be an appropriate fraction of their receiving/transmitting EM wave length.
What I'm interested in with this technology, is how you could 'tune' the material to receive/transmit in a broader frequency range than its 'natural' oscillation. That may be needed to make the antenna interesting for very broadband signals and tune-able equipment (like amateur radio transceivers or channel selectable broadcasting)
With 'normal' EM transmitting/receiving antennas we have various options to electrically tune the antenna but here you may have to dynamically 'shape' the material to permit a broader frequency range...
Well, for what it's worth, TFA says:
"In this work, the demonstrated ME antennas span a wide range of frequencies from 60MHz to 2.5GHz, which are realized by a geometric design of resonating plates that exhibit different mode of vibrations"
and
"It is notable that ME NPR antenna arrays with multiple frequency bands from MHz to GHz can be integrated in one wafer by designing the ME NPR with different lateral dimensions (or W), since the fr,NPR is inversely proportional to W27. This allows the broadband ME NPR antenna arrays on the same wafer, which compensates for the narrowband operation frequencies of ME antennas."
But really, lets start using these to shrink our ham radio rigs.
Actually, that does a lotta splainin.