Study On Array Virtual Extension And Beamforming

In order to increase the resolution without changing the size of the array antenna and process more signals,the method of array extension is generated.Among the existing extension methods,the interpolated transformation technique is used widely because of its advantages.Such as it can convert an arbitrary array into a uniform linear array(ULA)and the transforming matrix can be processed offline.With further research,it is found that problems of ‘angle sensitivity',‘interpolated step sensitivity',large calculations were exist when beamforming.In this paper,the improved interpolated array beamforming algorithm and the new method of array extension are proposed.The main work is as follows:(1)Aiming at the problem that interpolated transformation technique can not work effectively in a big area,and the burst interference can not be suppressed.The algorithm is proposed.The key operation is that the interpolated steering vector and covariance matrix are constrained by the transformation error and its covariance matrix respectively.In comparing with the existing algorithm,the new algorithm can suppress interference signal accurately and make the null deeper.Besides,it also increases the output signal to interference and noise ratio(SINR).(2)Aiming at problems that ‘angle sensitivity' and the sidelobe level is high during beamforming.Beamforming based on joint optimization for array interpolation is proposed.This algorithm is that in the case of minimizing the error of output signal power which is caused by transforming error,the sum of the sidelobe power is constrained to minimum by the angle weighting function.The new method can achieve low sidelobe beamforming in the large transformation area,and it overcomes the problems of high current taper,mainlobe extension,and inability to use the window function to suppress sidelobe in interpolated array.Besides,it has good reception and suppression effects for the spatial wave signals from the mainlobe and the sidelobe,respectively.(3)Aiming at problems that interpolated array has a large computation and sensitivity to transformation angle and interpolated step,a new array extension algorithm which is symmetric extension steering vector is proposed.Two properties that the conjugate of received data and the source covariance matrix is a real diagonal matrix are exploited to extend the dimensions of the covariance matrix.Numerical simulations show that the proposed algorithm is not affected by the angle range of transformation and the interpolated step and the complexity of array extension using this proposed algorithm is much lower.