Digital Beamforming Imaging Techniques for a Low Orbit Synthetic Aperture Radar Instruments

The current trend in spaceborne imaging radar is towards compact SAR systems produced at a relatively low cost. At the same time, there is a tendency towards instruments equipped with digital beamforming (DBF) capabilities on transmit and receiver, which is attributed to available digital technology. These two trends are (seemingly) contradicting, since digital beamforming facilitates an improved imaging performance but generally does not allow for size, complexity, or cost reduction. In this paper, we show that DBF may well be combined with compact SAR systems. It allows for the exploitation of elaborate imaging techniques customized to specific user requirements, which results in a simplified instrument hardware. The instrument and antenna design approach is for an L-band very low Earth orbit SAR system. Focus is put on the interrelation between the DBF imaging techniques and the instrument design. The calculated SAR performance is presented.