Research On Sparse Array Synthesis New Methods

The work of this paper is mainly divided into two aspects:the ultra-wideband(UWB)sparse array synthesis with minimum spacing control and pattern-reconfigurable sparse array synthesis with minimum spacing control.In the first part,a beam-scannable UWB sparse array synthesis method is proposed.The concept of design frequency is proposed to convert the beam-scannable UWB array synthesis problem into designing UWB sparse array at a single frequency.Combining the analytical method with the numerical optimization method based on convex optimization or the alternating projection method,the UWB sparse linear array or planar array with low sidelobe is designed.For sparse linear arrays synthesis,firstly,using the analytical array based on raised power series expression,an initial array with wideband performance is obtained by selecting appropriate parameters.Secondly,the iterative convex optimization method or the alternating projection method is used to fiurther optimize the position of the array element to reduce the sidelobe level.The optimization process needs to meet multiple constraints,including the first-order Taylor expansion accuracy constraints,the minimum element spacing constraints and the array aperture constraint.For sparse planar arrays synthesis,two kinds of analytical solution with wideband performance are introduced.The first one is the two-dimensional expansion of the raised power series linear array,the second is the planar array based on spiral.Then the planar array based on single-armed helix and double-armed helix are analytically optimized to obtain an initial array with a lower sidelobe level.Subsequently,on the basis of satisfying the first-order Taylor expansion accuracy constraint and the minimum element spacing constraint,the iterative convex optimization method is applied to multi-step perturbation of the array element position of the planar array to minimize the sidelobe level?In the second part,a multi-beam sparse array synthesis method based on convex optimization,which we call the alternating convex optimization method,is proposed.This method includes two constrained sub-problems.The sparse array is solved by alternately optimizing the excitation coefficient and the weight coefficient,wherein the array element spacing can be constrained in the convex optimization.The linear array with isotropic element is synthesized to verify the effectiveness of the proposed method in the main lobe shaping,sidelobe constraint,null control and minimum element spacing control.Considering the need of using antenna elements in actual engineering,and the mutual coupling effect between the units cannot be ignored,we add the actual antenna element structure to this method.We perform the alternating convex optimization method for more complex cylindrical conformal arrays.After model simulation and excitation re-correction,the experimental results show the stability and effectiveness of the proposed method in the synthesis of coupled multi-beam sparse arrays.