Multipath sensor based on GNSS for passive airborne surveillance

Passive radar systems are of great interest for several kinds of applications and therefore subject of actual research and development. One main application for passive radar systems is airborne surveillance, which includes the detection and tracking of airborne targets. Several passive radar systems based on terrestrial illumination have been demonstrated in the past. In passive radar applications based on satellite systems, a Global Navigation Satellite System (GNSS) can represent the radar transmitter, which illuminates the target, completed by a modified GNSS receiver, which analyses the radar signals. The advantages of this system would be the worldwide availability, the high number of transmitters and the coherent and well known signal structure. The main challenge in this system would be the extremely low signal power received on earth surface. In this paper, a multipath sensor for passive radar applications, which uses the Global Positioning System (GPS) L1 frequency as target illuminator, is demonstrated. Considerations about the expected signal power of multipath signals caused by a target are presented and confirmed through measurements. The main goal of this work is detecting, ranging and tracking a target in speed and distance over time.