Research Of Frequency Diverse Array Beamforming

Different from the conventional phased array transmitting carrier frequency,the frequency diverse array transmitting beam has range dimension dependence by adding small frequency offset to each array element transmitting signal carrier frequency,which has wide application potential in range interference suppression,range dimension transmitting energy control and other fields.The study of the emission beam pattern of frequency diverse array is of great significance for guiding the design and measurement of FDA antenna.Because some application scenarios need to realize 3D beam control in physical space,the related concepts of linear array are extended to uniform circular array.Based on the basic characteristics of frequency diverse array,the beamforming method of frequency diverse array and the uniform circular frequency diverse array are emphatically studied.The main research work and innovation of this paper are summarized as follows:(1)According to the angle and range coupling of the transmitting beam of the frequency diverse array,the beam pattern is S-shaped.The frequency offset controlled by different elementary functions can control the focus of the beam energy at the target point and effectively solve the coupling of the transmitting beam in the angle and range However,the low focusing resolution and high sidelobe level are not conducive to target positioning.Then two kinds of intelligent optimization algorithms,the frequency offset design based on artificial bee colony algorithm and genetic algorithm,are introduced to make the energy distribution of the beam pattern meet the point focus with high resolution at the target.Finally,the time-varying problem of frequency diverse array is discussed.(2)A uniform circular frequency diverse array model is proposed.Compared with linear array,it has the dependence of elevation and azimuth,which provides more freedom and possibility for radar application design.The expression of uniform circular array beamforming is derived.The effects of several typical nonlinear frequency offsets on the energy focusing of a uniform circular frequency diverse array are compared on a uniform simulation scale.Log + Sin-UCFDA side lobe level was the lowest,Square-UCFDA spot effect was the best,and Sin-UCFDA main lobe width was the smallest.Considering the distance,elevation and azimuth of the main lobe beam width,the number of side lobe,side lobe level,beam energy distribution and other factors,the corresponding frequency offset should be selected.(3)On the basis of the circular frequency diverse array emission model,a single antenna receiving frequency diverse array model based on circular array emission is proposed.The expression of receiving beam diagram is derived,and a design method of receiving weight vector for the formation is proposed based on convex optimization algorithm,and the effectiveness of the method is verified by simulation.