Researchers at MIT's Lincoln Laboratory have created a new radar system that allows them to "see" through walls.
The radar system works similarly to how human vision works. Just as waves of visible light bounce off of objects and hits the retinas in our eyes, the radar system delivers radio waves that bounce off targets and make their way back to the radar's receivers.
The reason we can't see through walls is because light can't pass through solid objects in the amount needed. In the case of radar systems, it's difficult to send strong signals that can pass through solid walls and then return through that solid wall to the receivers once again. The signal weakens as it makes its trip, and according to the study, 99 percent of signals don't make it back through the wall. If it does, the signal is weakened to about 0.0025 percent of its "original strength." Signal amplifiers can be purchased to solve this issue, but even so, figuring out the range, resolution and speed needed for real-time images is a challenge.
Despite this difficulty, MIT Lincoln researchers have managed to create a system that candetect certain objects on the other side of a solid wall, allowing them to "see" through these walls.
MIT's radar system, which consists of an array of antenna situated in two rows, one of which has eight receiving elements and the other 13 transmitting elements, is placed on a movable cart with some extra computing equipment. The transmitters emit waves of a certain frequency in the direction they desire, and signal amplifiers ensure that these waves make it through the wall and back.
But that's not all. The type of radio wavelength used is just as critical as how to send the signal. While longer wavelengths can travel through the wall and back with relative ease, they also need a larger radar system to identify human targets. So the team used S-band waves, which are shorter and have more issues with signal loss, but the radar tool can be kept smaller, which is important for this system to be used in the military. Signal amplifiers can handle getting the waves through the wall and back, but so far, 8-inch thick walls is all it can do.
Another issue is that the wall itself shows up as the brightest spot on the radar system, making it challenging to focus on what's on the other side of the wall. The MIT fixed this by using an analog crystal filter, which shows differences in frequency between the waves coming off of the wall and those coming from the target.
"So if the wall is 20 feet away, let's say, it shows up as a 20-kilohertz sine wave," said Gregory Charvat, study leader and technical staff at MIT Lincoln. "If you, behind the wall, are 30 feet away, maybe you'll show up as a 30-kilohertz sine wave."
The MIT radar system can be used as far as 60 feet away from the wall, and gives real-time picture movement behind the wall at a rate of 10.8 frames per second. When testing the radar system, the researchers were able to produce a blob of a human that shows up in bird's-eye-view.
For now, the system can only track moving objects instead of inanimate objects, but could still eventually be used in the military because even a human standing still moves a little bit, and this radar system can track that. But further research is required to make the blobs look more like the objects the waves are targeting.
Source: Dailytech.com
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