Technology that helps see through walls

Washington: Peering through thick walls is no longer science fiction but stark reality, thanks to a new cutting edge technology developed by scientists. MIT's Lincoln Lab researchers Gregory Charvat and John Peabody have built a system that can see through walls from some distance away, giving an instantaneous picture of the activity on the other side.

Their device is an unassuming array of antenna arranged in two rows - eight receiving elements on top, 13 transmitting ones below - and some computing equipment, all mounted onto a movable cart. But it has powerful implications for military operations, especially "urban combat situations", says project leader Charvat according to a Lincoln Lab statement.

Walls, by definition, are solid, and that's certainly true of the four- and eight-inch-thick concrete walls on which the researchers tested their system. At first, their radar functions as any other: Transmitters emit waves of a certain frequency in the direction of the target. But in this case, each time the waves hit the wall, the concrete blocks more than 99 per cent of them from passing through. And that's only half the battle.

Once the waves bounce off any targets, they must pass back through the wall to reach the radar's receivers - and again, 99 per cent don't make it. By the time it hits the receivers, the signal is reduced to about 0.0025 per cent of its original strength. But according to Charvat, signal loss from the wall is not even the main challenge. "[Signal] amplifiers are cheap," he says.

What has been difficult for through-wall radar systems is achieving the speed, resolution and range necessary to be useful in real time. "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. The Lincoln Lab team's system may be used at a range of up to 60 feet away from the wall. And, it gives a real-time picture of movement behind the wall in the form of a video at the rate of 10.8 frames per second.