基于非线性频偏的频控阵波束控制研究

与相控阵波束指向只具有角度相关性不同，频控阵波束图是时间、角度及距离的函数.这一特性在抑制距离相关性干扰等方面有着巨大的应用价值，但其方向图所固有的距离-角度耦合会带来新的频控阵波束控制问题.如何消除距离-角度耦合关系是实现波束精确控制及目标精确定位的前提.针对这一问题，提出一种基于可变加载约束的最速下降-线性约束最小方差（SD-LCMV）算法计算最优权矢量，同时将对数、三角函数、指数函数及倒数4种非线性频偏增量方式引入一维均匀线性频控阵（ULA-FDA）阵列，仿真验证应用4种不同非线性频偏的ULA-FDA阵列发射方向图的解耦性能.之后，采用多信号分类（MUSIC）算法仿真得到不同频偏情况下的MUSIC谱函数，对比分析4种频偏增量方式下的目标距离-角度二维联合估计性能.此外，仿真分析了sin-FDA阵列的接收机结构方向图特性及基于sin-FDA收发共形阵列的3种接收信号处理机制，从而验证了非线性频偏频控阵（FDA）阵列结构的有效性. 

Frequency Diverse Array Beam Control Based on Nonlinear Frequency Offset

Unlike the phased-array beam pattern with only angular correlation,the beam pattern of frequency diverse array (FDA) is a function on time,angle and distance.This feature provides a great application value in suppressing distance-related interference and other aspects,but the inherent distance-angle coupling of the beam pattern will bring about new frequency diverse array beam control problems.How to eliminate the distance-angle coupling relationship is the premise to achieve accurate beam control and precise target positioning.To solve this problem,an SD-LCMV (steepest descent linear constrained minimum variance) algorithm was proposed based on variable load constraints to compute the optimal weight vector.At the same time,the logarithm,trigonometric function,exponential function and reciprocal four nonlinear frequency offset increment methods were introduced into ULA-FDA array to verify the decoupling performance of the ULA-FDA array transmit patterns with four different nonlinear frequency offsets.Afterwards,the MUSIC (multiple signal classification) algorithm was used to simulate the MUSIC spectrum function under different frequency offset conditions,and the performance of the target distance-angle two-dimensional joint estimation under the four frequency offset increment methods was compared and analyzed.In addition,simulation was carried out to analyze the receiver structure pattern of the sin-FDA array and the three receive signal processing mechanisms of the sin-FDA transceiver conformal array.Results show the validity of the nonlinear frequency deviation FDA array structure.