FDM MIMO SAR Tomography

Abstract:
This work investigates a new concept to finely resolve the vertical structure of natural media by using a formation of spaceborne Synthetic Aperture Radars (SAR). The formation operates in Multiple Input Multiple Output (MIMO) mode by implementing a Frequency Division Multiplexing (FDM) access scheme, where all satellites transmit simultaneously on different frequency bands and receive the echoes scattered by the Earth’s surface in all transmitted bands. Fine vertical resolution is achieved by developing a novel approach to deploy the satellites in such a way that the resulting interferometric differential wavenumbers form an almost uniformly-spaced array of maximum length under the constraint of a given height of ambiguity and interferometric coherence magnitude. As a result, we show that formations of 4 or 5 satellites can be deployed to provide the equivalent of 17 and 26 monostatic acquisitions. The concept here developed to deploy the formation is referred to as Minimum Redundancy Wavenumber Illumination (MRWI), as it is shown to be a generalization to distributed targets of the principle of Minimum Redundancy Virtual Array (MRVA) used in array theory.