(Phys.org) -- A surveillance device that uses WiFi radio waves
has been devised to see through walls to detect, in military and
surveillance parlance, moving personnel targets. The device
serves as a radar prototype designed by two UK scientists at the
University College London (UCL). The scientists devised the
radar prototype as a way to track Wi-Fi signals in order to spy
through walls. Their device identifies frequency changes to
detect the moving objects. An important feature of their work is
that since the device itself does not emit radio waves, it
cannot be detected; it operates in stealth. Karl Woodbridge and
Kevin Chetty, researchers at University College London, designed
their detector to be able to use these signals. Chetty is a
lecturer in the Department of Security and Crime Science at
University College London; Woodbridge is with the schools
Department of Electronic and Electrical Engineering. The two
demonstrate what is called a passive radar system that can see
through walls using WiFi signals