Research On Robust Beamforming And Distributed Array Coherent Transmission

In the field of radar detection,high main lobe gain,robust to errors and strong antiinterference performance are the main goals of antenna beamforming algorithm design.Ideally,beamforming can align the nulls of the pattern to the direction of interference,so as to suppress interference.However,in the actual situation,due to the vibration or interference of the antenna platform,the interference deviates from the original null position and cannot be effectively suppressed,which affects the anti-interference performance of the system.On the other hand,the increasingly complex battlefield environment requires higher and higher performance of the radar system.The emerging distributed array radar system can obtain higher antenna gain in the coherent working mode than the single-aperture radar.The grating lobes or high side lobes caused by the sparse distribution in space contain a large amount of transmitted energy,which often results in a waste of energy.Therefore,it is necessary to deeply study the energy utilization improvement methods of coherent transmission in distributed array radar systems.In this paper,the main research is on the null broadening beamforming algorithm of the phased array antenna and the improvement method of the energy efficiency of the coherent transmission of the distributed array.Firstly,two beamforming algorithms are studied for the requirement of null broadening in the phased array antenna beamforming algorithm;then for the problem of improving the utilization efficiency of coherent transmission energy of distributed array,the method for using main lobe and grating lobe scanning to cover beam interval to improve transmission energy utilization is studied.The main research results and innovations of this article are as follows: 1.A robust null broadening beamforming algorithm is proposed.In this paper,we first make a deep study on a novel null widening beamforming method based on projection and diagonal loading.The algorithm uses subspace projection technology to preprocess the received signal,and then uses the diagonal loading technology to obtain a new covariance matrix for beamforming.In this paper,through theoretical analysis and simulation comparison,the principle of the algorithm is re-explained,and it is concluded that the null broadening of the algorithm is independent of whether the received signal contains the desired signal and the interference signal,and its performance is affected by the projection matrix.The algorithm has no compensation ability for array error and environment.When the preset interference extension area is mismatched with the real incident interference orientation and the array error exists,its interference suppression ability will decrease.In this regard,this paper improves on the basis of this algorithm,and proposes a robust nulling broadening algorithm.The algorithm uses the tapered sampling covariance matrix to perform the uncertainty set correction of the preset interference steering vector in the null broadening region,and then combines the tapering technique and the diagonal loading technique to reconstruct a new covariance matrix for beamforming.Simulation results show that the algorithm can effectively suppress fast moving interference in the presence of array error,and it has certain robustness to the array error and signal direction estimation mismatch.2.The method for improving the utilization efficiency of coherent emission of distributed array is studied.First,a distributed array coherent transmit signal model is established.Then,the characteristics of the grating lobe in the coherent transmission mode of the distributed array are analyzed and simulated.Finally,for the problem of improving the utilization efficiency of coherent transmission energy of distributed array,the method of using main lobe and grating lobe scanning to cover beam interval to improve transmission energy utilization is studied.