Radar that can 'see' through solid walls
Radar technology that can detect moving objects behind solid walls has been developed by MIT researchers.
The radar uses short radio waves and amplifiers, and once the signals are received, they get digitised into real-time video.
The scientists said it was possible to detect people, even those trying to keep still, behind a concrete wall from as far as 60 feet (18 metres)away.
One of the uses of the radar could be in combat situations.
A typical radar is able to "see" by sending radio waves that bounce off targets, then strike the radar's receiver - just like visible light bounces off objects and gets into our eyes, allowing us to see things.
As light cannot penetrate through solid walls, radio waves also get blocked by concrete, and whatever gets through is then blocked again on the way back.
The team dealt with this problem by using short waves known as S-band waves, and powerful signal amplifiers.
Gregory Charvat of the MIT Lincoln Lab, the lead scientist on the project, said that the hardest part for through-wall radar systems was achieving the speed, resolution and range necessary for generating a real-time video feed.
"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," said Dr Charvat.
During tests, the scientists were able to detect two people moving behind solid concrete and cinder-block walls, and a person swinging a metal pole.
They said that although the radar is designed to pick up moving targets, a person trying to stand still can never be perfectly still - so the radar would be able to detect small movements and display the object's location.
Once the signals come back and strike the receiver, they are digitised - and people appear as "blobs" in a live video feed.