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Internet-of-Things Radio Chip Consumes a Little Power to Save a Lot

Even as electronics become more efficient overall, many gadgets are also requiring power for a new use: to connect to the Internet. Engineers at MIT presented new research this week at the IEEE International Solid-State Circuits Conference that could help keep the power draw of connected devices in check.

Connected devices, which are seemingly everywhere these days, all require power to send data wirelessly. The need of each thing on the Internet of Things might be small, but the number of devices is expected to more than double between now and 2020 to more than 30 million, according to ABI Research.

Anantha Chandrakasan, professor of electrical engineering at MIT, presented a new transmitter design that reduces power leakage when a radio is in the off state by 100-fold. Even though it has ultra-low power needs, the system can still provide enough power for communication across different standards, including Bluetooth and 802.15.4.

“A key challenge is designing these circuits with extremely low standby power, because most of these devices are just sitting idling, waiting for some event to trigger a communication,” Chandrakasan told MIT News. “When it’s on, you want to be as efficient as possible, and when it’s off, you want to really cut off the off-state power, the leakage power.”

Chandrakasan said the key was to reduce the leakage of power in the transistor. Even when there is no charge applied to the transistor’s gate, it leaks some current. For devices that mostly sit idle waiting for a signal to power up, the slow leak can take a toll on battery life. (Limiting leakage was a main factor in two fundamental redesigns of transistors in computer processors.)

Arun Paidimarri, an MIT graduate student in electrical engineering and computer science and Nathan Ickes, a research scientist in Chandrakasan’s lab, applied a negative charge to the gate when the transmitter is idle, making the transistor a better insulator. Just a small negative charge, consuming just 20 picowatts of power, was able to save 10,000 picowatts in leakage.

“Ultralow leakage energy is critical for future sensor nodes that need the transmitter to be on only a very small percentage of time,” Baher Haroun, director of the Embedded Processing Systems Labs at Texas Instruments, said in a statement. Texas Instruments and Shell helped fund the work by Chandrakasan’s team.

Google AI Learns Classic Arcade Games From Scratch, Would Probably Beat You at Them

New artificial intelligence software from Google can teach itself how to play—and often master—classic 1980s Atari arcade games.

"This work is the first time that anyone has built a single general-learning system that can learn directly from experience to master a wide range of challenging task—in this case, a set of Atari games—and perform at or better than human level at those games," says one of the AI’s creators Demis Hassabis, who works at Google DeepMind in London. Hassabis and colleagues detailed their findings in in this week’s issue of the journal Nature. (And you can download the source code from Google here.)

The researchers hope to apply the ideas behind their AI to Google products such as search, machine translation, and smartphone apps "to make those things smarter," Hassabis says.

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Following Your Phone Friends Finds You

A relatively complete picture of our movements can be reconstructed from anonymized data generated by mobile phones by analyzing the movements of our social contacts, researchers say.

These anonymized details can also be used to reveal the nature of relationships between people, such as whether they are casual acquaintances, co-workers, or friends or family, scientists add.

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Apple to Spend Almost $2 Billion on European Data Centers

Hoping to better satisfy customers data privacy desires Apple looks likely to join other U.S. companies in flocking to Europe’s shores. On Monday, the U.S. tech giant announced plans to spend US $1.9 billion on new data centers in Denmark and Ireland that would go live in 2017.

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Wearable Vitals Tracker


In order to better care for patients, infants, and the elderly, research teams worldwide are investigating novel ways to continuously monitor people's health by tracking key life signs such as heart rate and body temperature. Such applications require sensors that are flexible and wireless for maximum comfort, self-powered to avoid replacement of batteries, and cheap enough to permit disposable use to ensure proper hygiene.

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A new wearable electronic device that is the brainchild of scientists at the University of Tokyo might fit those criteria. It’s an armband that combines a temperature sensor to measure body heat under the arm, a piezoelectric speaker to provide audible feedback, amorphous silicon solar cells for power, and circuits made of organic ink printed onto a plastic film. The same researchers previously developed flexible electronic skins with an eye toward covering prosthetic limbs and humanoid robots.

The team said the medical armband contains the first organic circuit able to produce sound, and is first device to incorporate an organic power supply circuit. These organic circuits increase the range of illumination at which the armband can operate by 7.3 times; this allows it to be used indoors.

The armband can emit an audible buzz when the body temperature it detects exceeds a preset limit. That temperature can be anywhere between 36.5 and 38.5 degrees Celsius. The scientists do not plan on incorporating a video display onto the armband. “We think sending information wirelessly is more important," said the study’s lead author, Hiroshi Fuketa.

The researchers noted the armband could incorporate other sensors to monitor heart rate, blood pressure, or moisture, as well as a flexible battery to store energy from the solar cells so the device can continue working after dark. The scientists will present the armband at the 2015 IEEE International Solid State Circuits Conference (ISSCC) in San Francisco on 24 February.

Photo: Sakurai Lab/Someya Lab

Building AI to Play by Any Rules

Computer algorithms capable of playing the perfect game of checkers or Texas Hold’em poker have achieved success so far by efficiently calculating the best strategies in advance. But some computer scientists want to create a different form of artificial intelligence that can play any new game without the benefit of prior knowledge or strategies. The software would face opponents after having only read the game’s rulebook. An AI that can adapt well enough to play new games without prior knowledge could also potentially do well in adapting to the rules of society in areas such as corporate law or government regulations.

This idea of general game-playing AI has gotten a big boost from the International General Game Playing Competition, a US $10,000 challenge that has been held as an annual event since 2005. The AI competitors must analyze the unfamiliar game at hand—say, some variant of chess—within a start clock time of 5 or 10 minutes. Then they each have a playclock of just one minute to make their move within each turn of play. It’s a challenge that requires a very different approach to AI than the specialized algorithms that exhaustively analyze almost every possible play over days or weeks.

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CogniToys Leverages Watson's Brain to Befriend, Teach Your Kids

Four years ago, IBM’s Watson utterly trounced a pair of very clever humans in a special tournament of Jeopardy! And by utterly trounced, we mean that Watson ended up with $77,147, while the nearest human only managed $24,000. Suck it, meatbags.

Since then, Watson has kept itself busy, most recently managing clinical trials at the Mayo Clinic. IBM has been desperately trying to get companies to integrate Watson into their apps, and last year, it held a contest for Watson app developers. One of the winners leveraged Watson to make smarter toys for fun, interactive learning, and you can now get a piece of this Watson-driven tech on Kickstarter.

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Optical Antennae Amplify LEDs for Fast Interconnects

Because lasers are fast—their transmission rate can reach 50 gigahertzthey are widely used for data transmission. Now researchers from the University of California at Berkeley and Bell Labs, Alcatel Lucent at Homdel in New Jersey have shown that by equipping light-emitting diodes (LEDs) with tiny antennae, they will be able to match and even surpass transmission speeds of semiconductor lasers, which would be especially useful over short distances. 

“If we push optical interconnects down to chip-scale, then we would want two things: First, the light source should be small physically, comparable to transistors, and secondly, they should be energy efficient,” says Ming Wu, who with Eli Yablonovitch, both at Berkeley, led the research team. They published this research in the February 10 issue of the Proceedings of the National Academy of Sciences.

Unlike lasers that produce intense focused beams of coherent photons by a process called “stimulated emission,” first seen in 1960, LEDs produce light by “spontaneous emission,” the ordinary light we see around us all the time.

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Coupling Microwaves to Optoelectronics With Sound

Sound is widely used for modulating light in optical communications or for controlling the output of lasers. The devices designed to do this, acousto-optic modulators, typically contain a crystal attached to a piezoelectric transducer. The sound waves propagating through the crystal modulate the intensity of light passing through it. But these devices are typically the size of a sugar cube, so integration with photonic chips is difficult. Also, their acoustic frequencies, limited to the megahertz range, make them unsuitable for high-speed optical communications.

Now, two researchers at the University of Minnesota have reported, in Nature Communications, how they overcame the frequency limitations of the transducer. They did it by reducing the size of the acoustic modulator and by integrating a nanophotonic circuit with the piezoelectric transducer on a single chip.

The logical approach was, of course, to look for a material with both good optical and piezoelectric properties. They used aluminum nitride, a piezoelectric material that fits the bill perfectly. It can easily be sputtered on silicon dioxide, has a high refractive index, and is a good conductor of sound waves. They deposited a 330-nanometer-thick layer of this material on a silicon wafer, then etched away some of the material to form a rib waveguide. The waveguide is a closed loop shaped like a racetrack; light is allowed to circulate around the elongated circle. A tiny piezoelectric interdigital transducer comprising parallel gold lines deposited on the aluminum nitrate emits sound waves in one of the racetrack’s straightaways.  

Because the gold lines in the transducer are only about 100 nanometers wide, they can generate sound waves with frequencies as high as 10 gigahertz.

“What is new in this research is that we reduce the wavelength of the sound wave to be even smaller than the wavelength of light,” says Mo Li, a coauthor of the paper and head of the electrical and computer engineering department’s nanophotonics and nanomechanics lab. The sound waves set up a traveling region of lower and higher density in the material; this region acts like a diffraction grate, bending the light sideways. Because the period of the grate is smaller than the wavelength of the light, the diffraction is very efficient.

This is not the only advantage of the on-chip design. The sound waves are, unlike conventional acoustic modulators, not bulk waves, but surface waves. “We do everything on a surface, and this is why we achieved a strong interaction between the sound and light,” Says Li.

Because they injected light into the racetrack and allowed it to resonate, the researchers were able to modulate the intensity of the light efficiently by injecting a 10-GHz signal into the acoustic wave transducer. Li explains that converting a microwave signal into modulated light will greatly increase the distance over which data-carrying microwaves can be transmitted. The light can transport the microwaves over much longer distances in optical fiber, with much lower signal loss and at a much lower cost, than transmitting them directly through air, says Li. “You only need a photodetector that can convert the light back into microwaves,” he adds.

With the recent breakthroughs in research into plasmons—surface waves of electrons induced by light on conducting surfaces—these waves’ interaction with acoustic surface waves might be an interesting new direction. “The challenge is to further reduce the sound wave to be of the same order as the wavelength of surface plasmon waves,” says Li. “This is not impossible, and you might find some interesting effects,” he says, adding that because both the sound waves and plasmons are surface waves, you will have a perfect overlap. 

Now the researchers’ goal is to increase the frequency of the sound waves to 20 GHz. Such higher frequencies will open up interesting possibilities for quantum computation, says Li. Sound waves will allow the coupling of optical qubits (photons) with phonons. Optical qubits are good for the transmission of data, while phonons, which arise at very low temperatures, are better suited for quantum processing.


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