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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.
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.
The Chu Limit applies to passive antennas. The antenna described in your citation isn't passive; that "non-Foster" term means it's an active antenna. The phys.org title implying some sort of breakthrough physics is click bait.
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.
"It was very good for receiving'
Same could be said for the ubiquitous ferrite loop antennae used for AM broadcast reception. They are magnetic field devices that can be quite small (a few cm) compared to medium wave wavelengths of several hundred meters. They are great for reception, but pretty much useless for transmitting. They also have very narrow bandwidth,. have two very sharp nulls in their reception pattern, and work progressively more poorly as the frequency increases.
You can't see ANYTHING from a car, You've got to get out of the goddamned contraption and walk...Edward Abbey
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?
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."