Research On Beamforming And Optimization Of A Nonlinear Frequency Diverse Array

Frequency Diverse Array(FDA)is first proposed by Paul Antonik and Michael C.Wicks at the IEEE radar conference in 2006.Because of its unique range-angle dependence and ability to reduce range-related interference,Frequency diverse array has attracted extensive attention of researchers in recent years.Different from the phased array radar(PA),the frequency diverse array will impose an additional frequency offset which far less than the carrier frequency between the array elements,that is,the carriers of the transmitted signals are not equal.So that the frequency diverse array can form a range-angle dependent beampattern.Because of this characteristic,the frequency diverse array has great potential in automatic beam scanning,range-angle joint location,target imaging and range-fuzzy clutter suppression.Based on the rangeangle dependent beampattern of frequency diverse array,this thesis focuses on the beamforming technology of nonlinear frequency diverse array.The main research contents and innovations are as follows:1.A frequency diverse array beamforming with tangent frequency offsets is presented.This thesis proves that the frequency diverse array can generate a perfect dot-shaped beampattern without trailing as long as the symmetry of the frequency offsets is ensured.To improve the peak sidelobe level(PSLL)performance of frequency diverse array with symmetric frequency offsets beampattern,a frequency diverse array beamforming with tangent frequency offsets is presented.Compared with the existing frequency diverse array with symmetric frequency,the beampattern formed by this method has advantages in the suppression of the peak sidelobe level and beamwidth.2.An optimization method of frequency diverse array beamforming with symmetrical tangent frequency offsets is presented.Firstly based on the distance-based Pareto Genetic Algorithm(DPGA),the elitist retention strategy and selection restrictions are introduced to make the algorithm have better convergence and higher population diversity.Then,by optimizing the symmetrical tangent frequency offsets,the optimal group of beampattern peak sidelobe level and the range dimension beamwidth is obtained,and a group of appropriate frequency offsets can be selected according to actual needs.Compared with that before optimization,the optimized perfect spot-beampattern beamwidth is narrower,and the peak sidelobe level is lower.