A central problem in applying superresolution to phased arrays is the knowledge of the "array manifold", i.e. the complete knowledge of the array outputs for a plane wave impinging on the array from all considered directions. This becomes a problem for large arrays where only subarray outputs are digitised. We investigate methods for determining an array manifold model with minimum knowledge of the subarray channels. The basic idea is to treat the subarray centres as phase centres of omni-directional "superarray" elements. Only the location of the centres and the gains have to be determined by calibration. The drawback of the simple model is that only a local superresolution property is achieved. By steering the look direction of the array local superresolution can be applied like a spotlight mode for any direction of interest. We investigate optimised subarray configurations which are determined by post-processing the subarray outputs.
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