A Research On Beamforming Algorithm Based On Virtual Antenna Array

With the rapid development of modern electronic information technology,array antenna is widely used in many fields such as wireless communication,satellite navigation,radar and so on.As the key technology of array antenna,adaptive beamforming can form nulls at the interference directions to suppress the interference.However,when the number of antenna elements is small,the performance of conventional beamforming algorithms is limited by the degree of freedom of the antenna array.Virtual antenna array can construct virtual elements,expand the array,increase the degree of freedom of the array antenna,and improve the anti-jamming performance of the array antenna,which has important research value.Therefore,this paper studies the beamforming algorithm based on virtual antenna array,the main research contents are as follows:(1).Aiming at the problem that the traditional beamforming algorithm can not suppress coherent interference when the interference power fluctuates greatly,this paper studies an anti-interference algorithm for coherent signals.Firstly,expands the array dimension by constructing virtual elements,and decoherence the expanded array.Then enhance the proportion of interference subspace to deepen the null of interference.The simulation results show that the improved algorithm can suppress the coherent interference without reducing the dimension.The antenna array with M elements can suppress the M-1 coherent interference.When the number of antenna arrays is five,the average null depth formed at four coherent interferences is-82.69 dB.(2).Aiming at the problem that the covariance matrix taper(CMT)algorithm will reduce the depth of null with null widening,when the interference disturbing.this paper studies a null broadening algorithm based on fourth-order cumulant,Firstly,reconstructs the fourth-order cumulant matrix of the array.And then taper this matrix to deepen and widen the null of interference.The simulation results show that the algorithm can deepen and widen the null of the interference at the same time.When the number of antenna arrays is five,the average null depth of the two interferences is-86.37 dB,and when the null depth is-60 dB,the null can be widened to 2.94 degrees.(3).Aiming at the problem that the null broadening performance of LCSS algorithm(Linear Constraint Sector Suppression)is limited by the degree of freedom of antenna array,when the interference disturbing,this paper studies a null broadening algorithm based on conjugate virtual expansion.According to the structural characteristics of uniform linear array,this algorithm constructs a virtual array element and increases the degree of freedom of antenna array,so it can construct sufficient linear constraint to widen the nulls in all interference directions.The simulation results show that the algorithm has good output performance when the interference angle is offset.