Low Sidelobe Beamforming For Uniform Circular Array Under Error Conditions

Uniform circular array can realize the advantages of simultaneous pitch and azimuth detection,360 degrees fuzziness in azimuth,isotropic of directivity,which has very wide application in radar,sonar,communication and other fields.Especially in the complex marine environment hydroacoustic detection,uniform circular array gradually becomes an important array form of seabed array sonar,submarine target sonar and even imaging sonar.However,compared with the linear array,the circular array has a higher sidelobe in the directivity function,which has the problem of weak interference suppression in practical applications.On the other hand,the errors caused by array placement and receiving system make the actual response of circular array different from the theoretical array manifold vector model,which has a great impact on the detection performance of circular array,such as sidelobe suppression and directional accuracy.Based on circular array beamforming,this paper establishes the array amplitude and phase error model,and studies the influence of circular array amplitude and phase error on the sidelobe suppression algorithm,so as to provide support for the improvement of circular array interference suppression and orientation performance.The main research contents and innovations of this paper are summarized as follows:1.Aiming at the problems of array element position error,amplitude and phase error caused by channel inconsistency and mutual coupling error between array elements in practical use,this paper establishes the error model of circular array elements,deduces the array guidance vector under the above error conditions,and analyzes the influence of array error on beamforming,The simulation analysis shows that the array error seriously affects the directivity and sidelobe height of beamforming.2.Aiming at the problem of high sidelobe in uniform circular array beamforming pattern,the sidelobe suppression algorithms of mode space conversion,virtual interference method and circular array pattern synthesis are theoretically deduced and simulated.After mode space conversion,the array manifold of the circular array has a van der Monde structure and can achieve a sidelobe suppression effect of about 8d B;The virtual interference algorithm adds a large number of virtual interference in the sidelobe area,and the sidelobe suppression level can reach about-30 d B;The array synthesis method with a given pattern can suppress the sidelobe and form a deep null to the interference in a specific direction.3.The sidelobe suppression model under the condition of array error is established,and the performance of sidelobe suppression algorithm under the condition of amplitude and phase error is studied.When the standard deviation of amplitude and phase error is0.1,the side lobe suppression effect of mode space conversion and virtual interference algorithm decreases;When the error standard deviation exceeds 0.2,the beamforming pattern is distorted and the beam cannot point to the desired azimuth.When the desired signal direction selected by the reference function is correct and there is no zero constraint,the array synthesis method of the given pattern is not affected by the amplitude and phase error;In the case of zero constraint,due to the mismatch of the guidance vector of the interference signal,the amplitude and phase error will cause the interference direction to no longer form a null.