Passive radar array with low-power satellite illuminators based on fractional Fourier transform

This paper addresses the detection of surface slow moving targets by means of an array passive radar based on low-EIRP satellite illuminators of opportunity. Particularly, the use of the receiving array of K elements is considered to provide increased detection capability for targets with limited radar cross section, together with the capability to estimate the target direction-of-arrival. A full processing scheme is proposed to exploit together both the long integration times and the multiple receiving elements. This includes a coherent space-time integration of the signal received at the K antenna elements during short frames, followed by an incoherent frame to frame integration. The proposed scheme is based on the fractional Fourier transform that is shown to map the signals into a natural rotated frequency-angle plane, where we can easily compensate the target Doppler frequency shifts available at the different antenna elements and temporal frames. Its effectiveness is shown by application to different synthetic scenarios, where the target detection is only achievable when all the possible integration gain is capitalized.