Research On Frequency Diverse Array Dot-Shape Beamforming Algorithms

In contrast to phased array radar,frequency diverse array(FDA)radar is a brand-new class of radar system that has a high degree of freedom,more variable beam scanning characteristics,and calls for more sophisticated array signal processing technologies.The beam pattern of a frequency diverse array is connected to distance,angle,and time because of the antenna’s modest frequency offset.It has a lot of potential for uses like interference suppression and radio frequency stealth.On the assumption of a linear frequency offset,there is a coupling between distance and angle in the frequency diverse array.The inability to focus the released energy is thus caused by the issue of periodic grating lobe radiation.The proposed nonlinear frequency offset has been successful in achieving decoupling,but the beam pattern of the frequency diverse array has been designed to a higher level due to the demands of tasks like accurate placement.In this dissertation,a thorough design is carried out for single-carrier frequency diverse array and multi-carrier frequency diverse array,respectively,in order to generate a beampattern with concentrated main lobe energy and low sidelobe level,under the condition of far-field target.The following is a summary of the main research efforts:Initially,the fundamental principles and mathematical framework of beamforming are outlined briefly.Subsequently,the array configuration and signal model of a frequency diverse array are examined.The directional properties of the frequency diverse array’s radiation pattern are then deliberated upon,and formulas detailing the periodicity of the pattern with respect to the angle,distance,and time dimensions are provided.Additionally,through simulation analysis,the impact of key array parameters on the form and efficiency of the frequency diverse array’s pattern is validated.Next,the article delves into the dot-shaped emission beamforming approach for addressing the issue of angle-distance coupling in frequency diverse arrays.By studying the frequency offset method,particularly the S-beam technique,the aim is to generate a dot-shaped beam.Four distinct frequency offset growth strategies,namely logarithmic growth deviation,square deviation,increased frequency deviation,and sine with cubic frequency partial solutions,are scrutinized and compared.Simulation outcomes reveal that while all four strategies successfully eliminate the periodicity of the S-beam,resulting in an approximately dot-shaped beam,there is a significant trailing effect associated with the beam.Finally,to solve this problem,the multi carrier array model is studied,and a square root frequency offset scheme is studied based on this.The simulation results show that this method can obtain a dot shape beam with concentrated energy and high resolution.On this basis,The LCMV algorithm is adopted to carry out adaptive beamforming,so that the dot-shape beam with better performance can be achieved.In addition,Grey wolf optimization(GWO)algorithm used to find the optimal weight vectors.By updating the positions of the alpha,beta,and delta wolves,the algorithm generates new weight vectors,which are then evaluated and compared with LCMV beamforming.Additionally,in order to maximize the suppression of sidelobe levels and achieve the focus of main lobe energy,this article divides the observation area and categorizes it as an energy distribution problem.In response to this issue,this article studies an optimization algorithm based on differential evolution,which solves frequency offset through iterative evolution.Comparing this method with genetic algorithm,interior point method,and other methods,simulation results have verified that the studied method can achieve better frequency offset performance.