Engineers Build Teeny-Tiny Bluetooth Transmitter That Runs On Less Than 1 Milliwatt (ieee.org) 43
Engineers at the University of Michigan have built the first millimeter-scale stand-alone device that meets Bluetooth Low Energy (BLE) specifications. "Consuming just 0.6 milliwatts during transmission, it would broadcast for 11 years using a typical 5.8-mm coin battery," reports IEEE Spectrum. "Such a millimeter-scale BLE radio would allow these ant-sized sensors to communicate with ordinary equipment, even a smartphone." From the report: The transmitter chip, which debuted last month at IEEE International Solid-State Circuits Conference, had to solve two problems. The first is power consumption, and the second is the size of the antenna. An ordinary transmitter circuit requires a tunable RF oscillator to generate the frequency, a power amplifier to boost its amplitude, and an antenna to radiate the signal. The Michigan team combined the oscillator and the antenna in a way that made the amplifier unnecessary. They called their invention a power oscillator. The key part of an oscillator is the resonant tank circuit: an inductor and a capacitor. Energy sloshes back and forth between the inductor's magnetic field and the capacitor's electric field at a resonant frequency determined by the capacitance and inductance. In the new circuit, the team used the antenna itself as the inductor in the resonant tank. Because it was acting as an inductor, the antenna radiated using changing magnetic field instead of an electric field; that meant it could be more compact.
However, size wasn't the only thing. Quality factor, or Q, is a dimensionless quantity that basically says how efficient your resonator is. As a 14-mm long loop of conductor, the antenna was considerably larger than an on-chip inductor for a millimeter-scale radio could be. That led to a Q was that was about five times what an on-chip inductor would deliver. Though it was a much more efficient solution, in order to meet BLE specifications, the team needed a better way to power the power oscillator. Their solution was to build an on-chip transformer into the circuit that supplies power to it. The transformer looks like two nested coils. One coil is attached to the supply voltage end of the oscillator circuit, and the other is attached to ground side. Pumping the transformer at a frequency twice that of the power amplifier wound up efficiently boosting the flow of power to the antenna.
However, size wasn't the only thing. Quality factor, or Q, is a dimensionless quantity that basically says how efficient your resonator is. As a 14-mm long loop of conductor, the antenna was considerably larger than an on-chip inductor for a millimeter-scale radio could be. That led to a Q was that was about five times what an on-chip inductor would deliver. Though it was a much more efficient solution, in order to meet BLE specifications, the team needed a better way to power the power oscillator. Their solution was to build an on-chip transformer into the circuit that supplies power to it. The transformer looks like two nested coils. One coil is attached to the supply voltage end of the oscillator circuit, and the other is attached to ground side. Pumping the transformer at a frequency twice that of the power amplifier wound up efficiently boosting the flow of power to the antenna.
Re: (Score:3)
Highly unlikely. They should maintain their nominal voltage for well over 10 years unused. This shit is real.
However horrifying.
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Battery size isn't mandatory.
PS: I don't actually know how big this thing is, you'd think they could have mentioned the size in such a long summary about something that stands out from the crowd due to its size, but nooooooo. Welcome to Slashdot.
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I already have coin cells that power ble for a shorter period, so why is this so surprising?
The power levels they mention make the claims realistic using fairly standard coin cells.
Re:Key word: could (Score:4, Interesting)
They actually make button cell batteries with different chemistry for long life.
Several, actually.
The poster child is Lithium Thionyl Chloride. (LiSOCl2)
Ten years or better in service. -55C to +85C (or still higher with a slightly tweaked chemistry.) Enormous capacity. (A size-D is 19 amphours at about 3.6V)
It's what they use in things like EPIRBs, underwater drones, and long life or extreme temperature IoT package tracking / environment monitoring tags.
Great! It will fit inside my ass. (Score:1)
Can you hear me NOW!?!?
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That already exists. https://www.amazon.de/Lovense-... [amazon.de]
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If that is your goal, on youtube you can find Naomi Wu doing a review of a "prison cell phone."
Better range than BLE.
Range? (Score:3)
FTA: "magnetic field instead of an electric field; that meant it could be more compact".
IIRC an antenna's magnetic field intensity falls off as the cube of distance, whereas the electric field falls off as the square. I'd be interested to know how the range of this new tech compares with a more traditional transmitter having similar output power.
Re: Range? (Score:1)
It's still using EM(photons), this is just the internal circuitry powering the antenna.
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Um, you can't have one without the other. They are simply talking about the near field, in the far field it's classical behavior.
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Both fall with the square of distance, a no brainer. There is nothing to "IIRC" ... as in recall. Just use a piece of paper and draw it up ...
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Actually both will fall with the cube of the distance. The problem is you do need to use your brain since the fields react differently between near field, far field and depending how the source of the radiation is setup.
If you don't use your brain at all then the GP was correct. Magnetic fields will fall off with the cube of the distance always. But then magnetic dipoles don't radiate and therefore don't generate a far-field response. If you think about it more then they are even more correct since the magn
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Actually both will fall with the cube of the distance. ....
That is correct, I copy pasted the wrong word, no idea why I wanted to copy cube, though, I guess I sometimes write qube
Pff... that's nothing! (Score:5, Funny)
I dunno why these Michigan bros are so excited. I mean, I talked to a homeless guy that told me all about how he had fillings that had microphones, their own power source and wireless transmitter. On top of that, they were installed over a decade ago. Seriously, these guys are behind the curve. ;)
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Wonder what TINYALAMO software with BLE (Bluetooth Low Energy) and allowed keystroke surveillance and injection did?
Re:Nothing new under the sun (Score:4, Funny)
Lol, I love it when young engineers "discover" decades old designs. Hell regenerative receivers are past the century mark now. Next up for discovery is the gunn diode and unijunction transistor. They are gonna shit themselves when they discover thin clients for the third time.
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Lol, I love it when young engineers "discover" decades old designs
They built a hell of a thing. It's incredibly small and incredibly low power.
But this is slashdot: the lace where the incompetent love to shit arrogantly on the competent.
Hell regenerative receivers are past the century mark now.
This is more involved than "simply" a transmitter with ositive feedback.
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Sometimes I think shitting arrogantly is the only pleasure some people have in life. Sad.
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Well, that and taking the moral high ground.
(and arguing about the air-speed velocity of an unladen swallow)
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I think this is a pulse power amplifier after the resonator circuit, driven at 2x frequency.
So fairly different, though both do use an inductor.
Great. (Score:2)
Even more connection issues with Bluetooth. Just what the world needs.