This paper presents a novel concept of a spaceborne Digital Beamforming (DBF) Synthetic Aperture Radar (SAR) based on a multi-beam reflectarray antenna. The proposed solution offers a number of advantages compared to more conventional DBF SAR systems using planar arrays or reflector antennas. The paper focuses on the spaceborne DBF SAR and discusses its architecture, system parameters and an imaging scenario. A reflectarray antenna design to be used in a combination with the considered imaging platform is presented in the paper. The reflectarray model is used to estimate DBF SAR performance characteristics discussed in the final part of the paper.

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This paper presents a novel concept of a spaceborne Digital Beamforming (DBF) Synthetic Aperture Radar (SAR) based on a multi-beam reflectarray antenna. The proposed solution offers a number of advantages compared to more conventional DBF SAR systems using planar arrays or reflector antennas. The paper focuses on the spaceborne DBF SAR architecture using a reflectarray antenna designed for the imaging platform. DBF SAR system parameters, an imaging scenario and a reflectarray antenna model are described in detail. The results of a performance analysis of the SAR system are presented and discussed in the paper.

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The paper presents the instrument concept and performance of a Ka-band single-pass interferemetric mission proposed for measuring topography and topographic changes. A formation flying constellation of two compact synthetic aperture radars (SAR) satellites equipped with innovative digital beamforming hardware and advanced operation modes is described.

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This paper reviews radar architectures that employ multiple transmit and multiple receive channels to improve the performance of synthetic aperture radar (SAR) systems. These advanced architectures have been dubbed multiple-input multiple-output SAR (MIMO-SAR) in analogy to MIMO communication systems. Considerable confusion arose, however, with regard to the selection of suitable waveforms for the simultaneous transmission via multiple antennas. In this paper, it is shown that the mere use of orthogonal waveforms is insufficient for the desired performance improvement in view of most SAR applications. As a solution to this fundamental MIMO-SAR problem we had previously suggested to exploit the special data acquisition geometry of a side-looking imaging radar equipped with multiple receiver channels in addition to appropriately designed waveforms transmitted by multiple antennas. Here, we extend this approach to a more general set of radar waveforms with special correlation properties that satisfy a short-term shift-orthogonality condition. We show that the echoes from simultaneously transmitted pulses can be separated if the short-term shift orthogonality is combined with digital beamforming on receive in elevation. This enables the implementation of a fully functional MIMO-SAR without correlation noise leakage for extended scattering scenarios.

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Synthetic Aperture Radar (SAR) operating at Ka-band frequency is increasingly being considered for spaceborne applications. The benefits are seen in the compactness of the instruments, the high bandwidth and resolution. Besides this the high carrier frequency facilitates single-pass interferometry by allowing for an accommodation of all transmitters and receivers on the same platform. This paper presents the instrument architecture and SAR performance for a system utilizing an advanced operational mode enabled through digital beamforming techniques.@en