Antenna Array Pattern Synthesis Based On Water Cycle Algorithm

In the information and communication fields such as radar and wireless communications,it is usually necessary to synthesis beams in special shape(flat-top pattern,cosecant-square pattern,low sidelobes,etc.).The pattern synthesis of array antenna is a very complex nonlinear optimization problem by adjusting parameters of simulation.Compared with traditional methods,intelligent optimization algorithms such as particle swarm optimization,genetic algorithm and invasive weed optimization are widely used in the field of antennas because of their high efficiency in solving complex practical optimization problems.Water cycle algorithm is a novel intelligent optimization algorithm that simulates the water cycle in nature and how streams and rivers flow into the sea.Besides the direct guide of global optimal solution(sea)for individual solutions(streams),it utlizes sub-optimal solutions(rivers)as indirect guide for individual solutions(streams)to reduce the inappropriate search.Its evaporation and rainfall process effectively prevent the algorithm from falling into many local optimal solutions.And fewer parameters make the algorithm easier to optimize.The water cycle algorithm is simple,easy to understand and has a strong search capability so that it has received extensive attention from scholars at home and abroad.However,the application of water cycle algorithm in antenna field is less.This thesis studies the application of water cycle algorithm in the pattern synthesis of array antennas.This thesis mainly studies the water cycle algorithm and the pattern synthesis of linear arrays and planar arrays.Firstly,the theory of linear arrays and planar arrays and the method for synthesizing the patterns of traditional array antennas are introduced.Then the Chebyshev-type patterns,flat-top patterns and cosecant-square patterns are synthesized by a traditional synthesis method,which builds theoretical foundation for later optimization.Secondly,water cycle algorithm is a novel intelligent algorithm.It has rarely been used in the field of antennas so far.Therefore,the principle,process and steps of the water cycle algorithm are described in detail.For comparison the particle swarm algorithm is briefly introduced and four verification functions are selected.These two algorithms are compared in aspects of the convergence speed,convergence accuracy and calculation time.It can be concluded that the water cycle algorithm has strong search ability and short calculation time.Thirdly,based on the theoretical analysis and algorithm analysis of the antenna array,the water cycle algorithm is applied to pattern synthesis.And the simulation results of seven Chebyshev pattern synthesis experiments verifies the effectiveness of water cycle algorithm in dealing with array antenna synthesis.At last,the flat-top directional pattern linear array and the cosecant-squared pattern linear array are designed,and the optimization result is substituted into the HFSS to present synthesised pattern.From the analysis of the horizontal plane and the elevation plane of the rectangular grid planar array and the triangular grid planar array,the water cycle algorithm is well used to optimize the amplitude and phase of the antenna array.Specifically,the flat-top pattern was shaped in the horizontal plane and the coplanar cosine was formed in the elevation plane.