Power/Performance Bits: July 2

Wi-Vi; new eyes for military.


Using low-power Wi-Fi to track moving humans
Based on a concept similar to radar and sonar imaging, researchers at MIT’s Computer Science and Artificial Intelligence Laboratory have created a system capable of seeing people through walls. Previous efforts to develop such a system have involved the use of expensive and bulky radar technology that uses a part of the electromagnetic spectrum only available to the military.

Now a system being developed by the MIT researchers could give everyone the ability to spot people in different rooms using low-cost Wi-Fi technology. The researchers said they wanted to create a device that is low-power, portable and simple enough for anyone to use, to give people the ability to see through walls and closed doors.

The system, called “Wi-Vi,” is based on a concept similar to radar and sonar imaging but in contrast to radar and sonar, it transmits a low-power Wi-Fi signal and uses its reflections to track moving humans. It can do so even if the humans are in closed rooms or hiding behind a wall.

As a Wi-Fi signal is transmitted at a wall, a portion of the signal penetrates through it, reflecting off any humans on the other side. However, only a tiny fraction of the signal makes it through to the other room, with the rest being reflected by the wall, or by other objects. They had to come up with a technology that could cancel out all these other reflections, and keep only those from the moving human body.

Off-the-shelf telecom technology new eyes for military
A new laser system developed of off-the-shelf telecom technology by researchers at the University of Michigan that can show what objects are made of could help military aircraft identify hidden dangers such as weapons arsenals far below.

The system emits a broadband beam of infrared light. While most lasers emit light of one wavelength, or color, super-continuum lasers like this one give off a tight beam packed with columns of light covering a range of wavelengths – a blend of colors. Because this beam is in the infrared region, it’s invisible to human eyes but can illuminate deep information.

The infrared contains what scientists refer to as the “spectral fingerprinting range” – frequencies at which they can detect echoes of the vibrations of the molecules that make up a solid substance. A substance’s spectral fingerprint reveals which wavelengths of light it absorbed, and which it reflected. Different substances absorb and reflect different wavelengths. So by shining the new laser on a target and analyzing the reflected light, the researchers can tell the chemical composition of the target.

These higher power lasers could give an aircraft flying at higher altitudes the capacity to illuminate a region with a brightness comparable to sunlight, and then image that region. Many chemical sensors in use today work at close range, but few, if any, can do the job from a long distance.

Beyond military applications, this device has the potential to improve upon today’s full-body airport screening technologies.

~Ann Steffora Mutschler

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