The performance of a Concentric Circular Antenna Array (CCAA) with robust techniques is presented in this paper. A CCAA geometry is chosen because of its symmetrical configuration which enables the phased array antenna to scan azimuthally with minimal changes in its beam width and side-lobe levels. The performance of CCAA system is degraded, if there is any disparity occur between the original signal direction and the steering direction of the beamformer. This performance degradation problem due to look direction disparity can be improved by using robust techniques. This paper proposes a technique, named variable diagonal loading (VDL) technique for CCAA system and compare the performance of the proposed robust CCAA processor with existing CCAA processors. The proposed robust CCAA beamformer enhanced the output power 28.9 dB, 9.34 dB and 1.63 dB at 10 disparity angle compared to the CCAA standard capon beamformer (SCB), robust SCB and existing novel loading technique. Numerical examples are presented to analyze the performance of the proposed robust beamformer in different scenarios.
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