Believe it or not, radar systems that can see through walls (aka "wall-through" radar systems) aren't exactly unheard of, it's just that most of them are burdened by limitations that make their use in real world settings pretty impractical.

But if the video up top is any indication, that could soon change in a big way. A team of researchers at MIT has developed a device that can provide its operators with real-time video of what's going on behind an eight-inch-thick concrete wall—from up to 60 feet away.

According to engineer Gregory Charvat, staff scientist at MIT's Lincoln Laboratory and leader of the project, the major hurdles for previous wall-through systems (which, historically speaking, have been developed primarily for use by police, special forces, and emergency services) have been speed, resolution, and range.

"If you're in a high-risk combat situation, you don't want one image every 20 minutes, and you don't want to have to stand right next to a potentially dangerous building," Charvat says.

Charvat's device is structured around what is known as a multiple-input multiple-output (MIMO) phased array radar system. Here's how it works:

The "multiple output" portion of the technology uses a row of thirteen transmitting elements to pump out S-band radio waves (these have a wavelength comparable to a wireless internet signal) towards on opaque obstacle (which, in this case, is a concrete wall).

Very few of these S-band waves will make it to the other side of the wall, and fewer still will make their way back through the obstacle after reflecting off any objects of interest (i.e. people). The waves that do manage to make it back through the wall are detected by a row of eight receiving antennae, which feed the "multiple input" channel of Charvat's MIMO device.

Waves that bounce off the wall and return to the device are then differentiated from waves coming from the target behind the wall. "So if the wall is 20 feet away, let's say, it shows up as a 20-kilohertz sine wave. If you, behind the wall, are 30 feet away, maybe you'll show up as a 30-kilohertz sine wave," Charvat explains. This information is then digitized into a top-down, real-time, two-dimensional video depiction of movement taking place on the other side of the wall.

Scientists at MIT have developed a device that allows you to see through concrete wallsS

If you've played video games like Metal Gear Solid or Grand Theft Auto, the radar GUI used in these games is very similar to the type of top-down imaging we're talking about here, only with Charvat's system, people show up as amorphous "blobs" instead of clean, circular blips.

Charvat says he and his team are working on this last bit: "what we would like to do in the near future is...implement a detection algorithm where, instead of seeing the blobs, you would see little crosses or squares."

Charvat and his team recently presented a paper describing their device (doi: 10.1109/ARRAY.2010.5613314) at the IEEE International Symposium on Phased Array Systems & Technology

[Spotted on Popular Science]
Video by Melanie Gonick via MITNewsOffice
Hat tip to Barbara!