Digital Beamforming for Spaceborne ReflectorBased Synthetic Aperture Radar, Part 1 Basic Imaging Modes

Abstract

Deployable reflector antennas illuminated by a digital feed array enable spaceborne synthetic aperture radar (SAR) systems capable to image an ultra-wide continuous swath at fine azimuth resolution. This is facilitated by the use of dedicated operation modes and by multi-dimensional digital beam-forming techniques. This paper is intended as a tutorial, where focus is put on the required on-board functionality, operational techniques, and the digital beam-forming aspects, for which a rigorous mathematical description is included. To maintain general validity, the functional implementation for the various modes is detailed, thus avoiding restricting the description to a specific realization. The reader is assumed to be familiar with the general concept of synthetic aperture radar, and otherwise referred to literature \cite{Moreira13} for a general introduction. The approach followed here is to start with a basic simple operation concept (part I) and then move to more advanced modes (part II and III) successively increasing the complexity; the mathematical description follows the same approach.