High-Resolution Stripmap SAR Imaging

SAR imaging method comprising performing N SAR acquisitions in stripmap mode of areas of the earth's surface by means of a synthetic aperture radar (20) that is transported by an aerial or satellite platform and which comprises a single, non-partitioned antenna and a single receiver coupled to said single, non-partitioned antenna, N being an integer greater than one;

• wherein the single, non-partitioned antenna of the synthetic aperture radar (20) is associated with a nominal pulse repetition frequency;
• wherein all N SAR acquisitions in stripmap mode are performed using one and the same predetermined elevation angle with respect to the nadir of the synthetic aperture radar (20) so that said N SAR acquisitions in stripmap mode all regard one and the same specific swath of the earth's surface;
• wherein each SAR acquisition in stripmap mode is performed using a respective squint angle with respect to the flight direction of the synthetic aperture radar (20), said respective squint angle being different from the squint angles used for performing the other N-1 SAR acquisitions in stripmap mode;
• wherein each performed SAR acquisition in stripmap mode comprises respective radar transmission and reception operations that:
• are time interleaved, individually or in groups, with single, or groups of, radar transmission and reception operations of the other N-1 SAR acquisitions in stripmap mode performed;
• and
• comprise the transmission and reception of respective radar beams in respective acquisition directions that are defined by the predetermined elevation angle and by the respective squint angle used for said SAR acquisition in stripmap mode, thereby resulting in that said respective acquisition directions are parallel to each other and not parallel to the acquisition directions of the other N-1 SAR acquisitions in stripmap mode performed;
• wherein the radar beams transmitted and received in two radar transmission and reception operations performed in two immediately successive time instants and related to two different SAR acquisitions in stripmap mode are contiguous along the azimuth, thereby increasing the integration times with respect to those obtainable via any one of the N SAR acquisitions in stripmap mode performed;
• and wherein the radar transmission and reception operations are performed by:
• using an operational repetition frequency that is N times greater than the nominal pulse repetition frequency;
• or
• varying the squint angle used in pulse repetition interval blocks;
• the method further comprising generating SAR images of areas of the specific swath on the basis of all the N SAR acquisitions in stripmap mode performed, said SAR images having an azimuth resolution that is enhanced by a factor up to N with respect to a nominal stripmap azimuth resolution that is equal to half the physical or equivalent length along the azimuth direction of the single, non-partitioned antenna of the synthetic aperture radar (20).