Study On Conformal Array Beamforming Based On Virtual Array

Conformal array is usually allocated in the surface of aircraft which has high speed motion.Compared to common linear array or planar array,conformal array not only has wider beam scanning range,but also has a low profile,and won't affect the aerodynamic performance of the aircraft,so it has very broad prospects in application of spaceborne,airborne,missile and other mobile platforms.Conformal array,however,because of its unique array form,makes the analysis and research more complicated than linear array and planar array,and many of the existing beamforming algorithm cannot be used directly.Virtual array is a new technology based on smart antenna technology,data for a virtual array are required to be obtained using transformation of real data,to achieve a transformation from the original array to virtual array signal processing.When the interpolation technology is applied to virtual array beamforming,the beam pattern of virtual array suffers from high sidelobe problem;and due to the mapping errors,the form of the virtual array is important,and the method is limited to small angle range as well.This dissertation mainly studies on these problems on the conformal array beamforming.To solve the high sidelobe problem,the sparse constraint method is applied to virtual array beamforming algorithm,to suppress the sidelobe of virtual array beam response;however,the sparse constraint method suffers from a low nulling in the direction of interference problem,so a sparse constraint method with differnt weights,based on MUSIC algorithm is proposed,to get lower sidelobe and deep nulling in the direction of the interference as well.The interpolation mapping errors will affect the performance of virtual array beamforming,especially at wide angles.In this way,we analysis the factors that affect the mapping errors,then present the second method by optimizing the array weights to constrain the mapping errors.The key feature of this algorithm is keeping the orthogonality between the mapping errors and the weights,which can be achieved by loading the covariance matrix of the mapping errors on that of the signals.By doing this,the beamforming performance of the virtual array can be improved,even for relatively large mapping errors.