Multi-beamforming And Optimization Of Phased Array Antenna

Multi-beamforming technology is to form multiple beam simultaneously based on beamforming technology.Phased array radar can realize the function of spatial filtering more conveniently by forming multiple independent beams.With the continuous development of digital technology,multi-beamforming technology has been used more widely.This paper focuses on the research of digital multi-beamforming technology.The main works are as follows.1.The shared-aperture multi-beam forming technology is studied.Firstly,the shared-aperture technology of multi-beamforming based on iterative FFT algorithm is introduced.The theoretical derivation and simulation analysis of the algorithm are carried out and the simulation results show that two beams with similar performance can be obtained.Due to the solution obtained by iterative FFT algorithm is not the optimal solution,an improved method which using genetic algorithm to optimize element excitation is proposed in this paper.The simulation results show that the performance of the algorithm is improved but the peak side lobe level of the two sub-arrays still needs further optimization.A shared aperture of multi-beamforming based on binary invasive weed optimization algorithm is proposed to solve the problem of high side lobe level.The elements position is also taken as optimization variable and the peak side lobe level is taken as optimization objective.The simulation results show that the optimization effect of binary invasive weed optimization algorithm is better than that of iterative FFT algorithm.At the same time,this paper also proposes a shared aperture method of multi-frequency to solve the problem of narrow beam bandwidth in existing research.The different beam frequency is taken as constraints.The position and spacing of array elements are taken as optimization variables simultaneously.This paper uses simulated annealing as optimization algorithm for the invasive weed optimization algorithm is not suitable for multivariable optimization.The simulation results show that the algorithm can form two beams with different frequencies and directions,and the side lobe levels of the two beams are further suppressed2.The multi-beamforming technology based on time modulated antenna array is studied.The time modulated antenna array introduces time dimension to the phased array,and it can form more beams than the phased array with same number of elements.Invasive weed optimization algorithm is applied to multi-beamforming technology of time modulated antenna array.The peak side lobe level of the radiation pattern is taken as the objective function and the control time sequence of each element switch is taken as optimization variables.At the same time,this paper proposes an improved method of combining invasive weed optimization algorithm with particle swarm optimization algorithm to solve the problem of poor local search ability of invasive weed optimization algorithm,and compares it with other algorithms.The simulation results show that the improved invasive weed optimization algorithm can get lower objective function values and the performance of algorithm has been further improved.3.The nulling technology of multi-beamforming is studied.In order to solve the problem of lack of information exchange in the evolution of invasive weed algorithm,an improved invasive weed algorithm combined with genetic algorithm is proposed in this paper.In the process of the seed diffusion,the crossover operation of genetic algorithm is introduced to improve the weed individuals.At the same time,the improved invasive weed optimization algorithm is applied to the technology of nulling generation based on pattern synthesis of antenna array.The simulation results show that the improved invasive weed optimization algorithm is superior to the conventional algorithm in performance.Combining with the harmonic beamforming technology of time modulation antenna array,the nulling in the specified direction can be achieved while forming multiple beams.