Optimal trajectories for range resolution improvement in multi-PCL SAR

In this paper the problem of multiple passive coherent location (PCL) radar systems mounted on moving platforms for range resolution improvement is addressed. Specifically, enabling them to be also used for imaging purposes. Constellations of low-cost ultra-light platforms constitute an extremely appealing solution for future surveillance and reconnaissance systems. These platforms exploit a common transmitter of opportunity, but they observe the area of interest with slightly different incident angles. As a consequence, the corresponding ground echo signals result shifted in the K-space, thus enabling a range resolution improvement. In this paper it is shown how the relative shift of these echo signals varies (in general) during the synthetic aperture and it is also described how this varying shift impedes proper imaging. In addition, optimal trajectories for the different platforms are derived which guarantee a constant K-space signal occupancy during their motion. Finally, an analysis is performed to assess the effects of non-ideal flown trajectories.