Passive radar for micro-doppler based helicopter classification : theory and demonstration

In recent years there has been a growing interest on the capability of using illuminators of opportunity for radar purposes. Possible illuminators are systems deployed generally for communication purposes, for example Digital Video Broadcasting-Terrestrial (DVB-T), FM Radio and Global Navigation Satellite Systems (GNSS). A system exploiting the energy transmitted from these non-cooperative transmitters is called Passive Bistatic Radar and has been successfully investigated in different applications. Advantages of this kind of technology includes: reduction in costs, stealth systems, frequency allocation free and the capability to having information from a portion of the spectrum that was unavailable in the past. In particular the alternative use of Global Navigation Satellite System (GNSS) has recently initiated a number of studies that aim to exploit this source of illumination for passive radar. In this paper we investigate the concept of a GNSS based passive radar for extraction of micro-Doppler signatures from helicopter rotor blades with the aim of identifying and characterising these kind of targets. The proposed system, exploits forward scattering enhancement and bistatic geometry to measure the micro-Doppler signature of the helicopters rotor blades, providing unique information about the target. The theoretical concepts will be backed up by experimental validation of our method with real data acquired from helicopter