Staggered SAR Range Ambiguity Suppression with Quasi-Orthogonal Signals

Nowadays synthetic aperture radars (SAR) carried by airborne and small satellites are actively used during all-weather and noctidial observation missions of large-scale land and ocean areas. SAR swath size is directly dependent on the installed antenna size which set bounds to minimal carrier size and weight characteristics. Due to the cyclic varying of the emitted pulse repetition frequency, a staggered SAR swath is widening without changes to the utilized antenna dimensions. However, a constraining factor is present in a form of occurring range ambiguity. This is especially relevant for spaceborne and airborne long-range SAR systems, in which 10 to 15 probing pulses could be transmitted before receiving the signal, reflected from the desired area. In this paper, a series of range ambiguity suppression techniques are examined and their key characteristics are presented. In addition, a new modification to the existing technique of modulating probing pulses by quasi-orthogonal signals is presented.