Multi-objective Optimization Design Of Fragment-Type Antenna Structures

In electromagnetic field,the optimization design of antenna structure has always been a research hotspot.In recent years,the topology structure has gradually become a key research direction because of its easy impedance matching,good filling efficiency,and design freedom in a given design region.Meanwhile,the design of antenna structure is mostly a Multi-objective Optimization Problem(MOP),and Multi-objective Evolutionary Algorithm(MOEA)is gradually attracting attention from antenna engineers since its potential in solving complex engineering problems which are multi-variable,multi-objective,non-differentiable,highly nonlinear,and multiple maximum.MOEAs also have strong global searching capability and multiple Pareto optimal solutions can be obtained during single optimization.In this paper,we will take the fragment-type topology antenna structure as the research object,and focus on the electromagnetic numerical simulation of such structure,the improvement of optimization method and the engineering design based on the improved algorithm.The research content is mainly divided into the following three parts:1.Electromagnetic numerical simulation of fragment-type antenna structure.In this paper,Finite-Difference Time Domain(FDTD)algorithm is used to simulate the fragment-type antenna structure.The accuracy of FDTD source code is verified by comparing with the High Frequency Structure Simulator(HFSS)and measurement results;Then the impact of different sizes and different overlap sizes on the simulation results in fragment-type structures was first explored;Finally,FDTD method was proved to be highly efficient,especially when the design matrix was large enough,It shows great potential.In addition,this paper also introduces the efficient algorithm framework of FDTD combined with multi-objective optimization technology.2.Modified MOEA/D-GO-II is introduced in this paper.Novel boundary-based MOEA/D-GO-II is proposed based on MOEA/D-GO-II,combining a boundary-based weighted sum filtering operator and a boundary-based median filtering operator,ensuring the connectivity of fragment structure and peripheral structure.At the same time,boundary-based MOEA/D-GO-II can obtain more optimal solutions because of the effective reduction of the effect of filtering operator on population diversity.3.Engineering design based on boundary-based MOEA/D-GO-II.Boundary-based MOEA/D-GO-II is used to successfully design the highly isolation structure for two MIMO PIFAs(Planar Inverted-F Antennas)operating at 2.345 GHz-2.36 GHz with a center distance of only 15 mm.Compared with previous research results,the design of this paper shows better front-to-back ratio and wider relative bandwidth,and increases the number of optimal solutions.Then,boundary-based MOEA/D-GO-II is also used to design the band-stop filtering structure for band notched antenna.The optimized fragment-type band-stop filter works in the 5G band operating at 3.3GHz-3.6GHz,and shows great out-of-band rejection.Through the above-mentioned optimization design of fragment-type antenna,it is proved that the proposed boundary-based MOEA/D-GO-II can obtain more optimal solutions and have certain potential in the field of engineering applications,providing a new idea for the optimization design of fragment-type antenna structure.