British engineers from University College London, have developed a passive radar system that allows you to see through walls, through the use of signals Wi-Fi, which are generated by wireless routers and access points.
This system was developed by Karl Woodbridge and Kevin Chetty. It consists of two antennas, the signal processing apparatus (computer), and its dimensions do not exceed the suitcase. Unlike conventional radar, which generates radio waves and then measures the reflected signals, the effect of this system can not be detected.
The principle of passive radar is pretty simple. In any place, equipped with Wi-Fi, you are exposed to a continuous bombardment of radio waves in the 2.4 GHz and 5 GHz. When these waves reach a moving object, the frequency change (Doppler effect). Passively listening to signals Wi-Fi, Woodbridge and Chetty learned reconstruct the image of any objects or people that move across the wall.
Essentially, this radar system that captures radio waves that are emitted by an external Wi-Fi router, instead of having to create them yourself.
During testing, these passive radar systems were able to determine the location, speed and direction of movement of the person through a brick wall thickness of 30 cm only problem systems based on the Doppler effect, is that they only work with moving objects. The hypothetical burglar or action can cheat the system just froze in place. But engineers believe that the improved system will be able to increase its sensitivity, which will capture even the movement of ribs inhalation and exhalation.
Scope of application, as can be understood from the description - it’s mostly military intelligence. The Ministry of Defence of the United Kingdom is already investigating the use of passive radar for military operations in urban environments. In addition, this radar may be used to track the movements of children (or aged) at home. Presumably, the development of a sufficiently sensitive equipment (and with plenty of routers Wi-Fi), you can even make videos in X-rays.