New Synthesis Techniques For Low Sidelobe Array Antennas Based On Subarray Partitions

With the improvement of anti-jamming performance,low sidelobe level(SLL)antenna arrays are widely used in high performance radar and communication systems.At present,in order to obtain higher radiation gain,it is necessary to increase the aperture and the number of elements in the antenna array.However,antenna arrays with a large number of active elements are complex and costly.In recent years,in order to reduce the complexities and costs for antenna arrays,subarray technique has been proposed to convert the design of element excitations to the simultaneous designs of subarray partitions and excitations,which reduce the number active elements in antenna arrays.Those synthesis problems for antenna arrays based on subarray partitions are mix real and integer optimization problems in mathematics,which can hardly be solved by conventional methods.Therefore,synthesis of low SLL antenna array based on subarray technique is of great theoretical significance and engineering value.In this dissertation,some new hybrid techniques for synthesizing subarrayed low SLL antenna arrays are concerned.The author's main works and contributions are summarized as follows.1.A novel hybrid differential evolution(DE)algorithm integrated with convex programming(CP)method is proposed.First,the mathematics model for the optimization problems which can be solved by the proposed DE-CP method is established.In the low sidelobe arrays synthesis problems,variables are divided into two parts.The DE algorithm is used to handle the variables corresponding to layouts only,e.g.elements locations and subarray partitions.Then,the relationship is established between the optimal solution in each convex subproblem and fitness function in the DE algorithm.An appropriate fitness function is defined in the hybrid method according to the relationship.Finally,peak SLL are optimized by the proposed hybrid method for symmetrical and asymmetrical patterns in linear sparse arrays with optimized element excitations,linear sparse arrays with extended elements and subarrayed monopulse linear ararys,and specific optimization models of the four examples are given.Compared with other existing methods,better solutions can be obtained by the proposed DE-CP method,due to convexity of those problems exploited sufficiently.2.A novel technique for synthesizing subarrayed monopulse arrays with contiguous elements is proposed.In the existing subarrayed monopulse arrays,the elements grouped in the same subarrays are irregular and noncontiguous,which will increase complexity of the feeding networks because of the circuit crossing.In order to overcome the limitation,the synthesis technique for monopulse subarrayed antenna arrays with contiguous elements is proposed.First,new constrained optimization models are established to represent the contiguously subarrayed low sidelobe monopulse antenna arrays synthesis problem.Then,by defining an appropriate fitness function to convert the problem into an unconstrained one,the problem is efficiently solved by the differential evolution algorithm under successful parent selecting framework(SPS-DE).Finally,four examples are synthesized to indicate the effectiveness of the proposed technique.The first example is synthesizing subarrayed monopulse linear arrays with noncontiguous elements which demonstrate effectiveness of the SPS-DE algorithm compared with the existing results.Then,two monopulse arrays are synthesized by proposed contiguous elements subarray techinique,in which sum patterns are fixed by Dolph-Chebyshev synthesis or jointly optimized by SPS-DE.The results indicate the necessity of the optimized sum pattern.Finally,synthesis of low sidelobe monopulse subarrayed conformal circular arc arrays with contiguous elements is discussed.Numerical results indicate the proposed synthesis technique based on contiguous subarray is suitable for synthesizing low sidelobe monopulse linear and conformal circular arc arrays.3.A novel hybrid method combining iterative Fourier technique and fuzzy C-menas algorithm(IFT-FCM)is proposed.The existing methods for synthesizing low sidelobe linear arrays based on subarrays with contiguous and noncontiguous elements are time consuming,and require a lot of prior knowledge.In order to overcome these drawbacks,a novel IFTFCM is proposed.First,the FCM is used to establish the relationship between subarray partitions and element excitations in the linear arrays,and integrated into IFT.Then,an auxiliary excitation sequence based on element excitations and locations is established to make the elements contiguously in the same subarray in the syntheses of single sum or difference pattern.Finally,four examples,including uniformly subarrayed linear arrays with low SLL sum pattern,nonuniformly noncontiguously subarrayed linear arrays with low SLL sum and difference patterns,and nonuniformly contiguously subarrayed linear arrays with low SLL monopulse patterns are synthesized.Numerical results indicate that the proposed hybrid iterative method is much faster than the state-of-art methods with the same or lower peak SLL.