WiFi can be used to see through the wall

British engineers from University College London have developed a radar system that can see through walls using the WiFi signals generated by wireless routers. The system, devised by ‘Karl Woodbridge’ and ‘Kevin Chetty’, requires two antennas and a signal processing unit, and it can be place in a suitcase. Wi-Fi radio signals are found in 61 percent of homes in the U.S. and 25 percent worldwide. Unlike normal radar, which emits radio waves and then measures any reflected signals, this new system operates in complete stealth. The radar itself does not emit any signal and thus cannot be detected, making it ideal for spying or military operations.

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1. MOVING SUBJECT

When Wi-Fi radio waves bounce off a moving object, their frequency changes. If, for example, a person is moving toward the Wi-Fi source, the reflected waves’ frequency increases. If a person is moving away from the source, the frequency decreases.

2. REGULAR OL' ROUTER

A Wi-Fi Internet router already in the room fills the area with radio waves of a specific frequency, usually 2.4 or 5 gigahertz.

3. BASELINE SIGNAL

One antenna of the radar system tracks the baseline radio signal in the room.

4. SHIFTED SIGNAL

A second antenna detects radio waves that have reflected off of moving objects, which changes their frequency.

5. PERP, SPOTTED

By comparing the two antennas’ signals, the computer calculates the object’s location to within a few feet as well as its speed and direction.