Spotlight MUSIC: super-resolution with subarrays with low calibration effort

A central problem in applying super-resolution 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. In the paper methods for determining an array manifold model with minimum knowledge of the subarray channels are investigated. The basic idea is to treat the subarray centres as phase centres of omni-directional 'super-array' 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 super-resolution property is achieved. By steering the look direction of the array, local super-resolution can be applied like a spotlight mode for any direction of interest. The local super-resolution property has the advantage of suppressing uninteresting sidelobe sources and thus simplifying the super-resolution procedure due to the lower target number. Optimised subarray configurations which are determined by post-processing the subarray outputs are investigated. Using the MUSIC method as an example it is shown that no significant advantage can be gained with the optimised approach.