Abstract:
Conventional radar systems use a dedicated transmitter for relaying signals which after reflections from the target are processed by the receiver. Passive radars on the other hand, are a class of radar systems which do not require an active transmitter but rather detect objects and their motion using non-cooperative sources of illumination such as communication signals (GSM, FM, etc). These systems provide numerous advantages over active radar systems. Since a dedicated transmitter is not required, Passive radars are comparatively inexpensive and are more energy efficient. Development of precise passive radar systems has, therefore, been a field of active research. Few such systems are already being deployed in various military and security applications.
Our goal for this project was to provide a proof of concept for the applicability of the Wi-Fi signals as the illuminator of opportunity in a passive radar systems. Wi-Fi networks are common throughout urban environments and hence, are an excellent candidate for passive radar applications in such places. The feasibility of Wi-Fi has been studied extensively and experimental results show that it is a viable illuminator. Several techniques have been proposed for motion detection. Our system is based on extracting the Doppler shift information from the Wi-Fi packets received after being reflected from the target. We tested our system with IEEE 802.11 standard and we were able to detect motion in surrounding environment. We were also able to provide a rough estimate of direction of motion.
