| Antenna-array is a necessary medium for achieving the communication environment and information exchange,and it has an irreplaceable role in the vehicle wireless communication system.Owing to the increasing complexity of road electromagnetic environment and the continuous improvement of miniaturization and integration requirements,the internal and external interferences have become key technical challenges restricting further development of antenna-arrays.The effective interference suppression produces very important research prospects in the vehicle wireless communication system.Due to the appearance of the internal and external interferences,the radiation performances of arrays become deteriorated and the anti-interference ability is reduced.Therefore,improving the desired radiation performance of arrays and achieving the anti-interference ability have become the key issues that need to be solved urgently in the current internal and external interference suppression,which has great significance for ensuring the communication environment and information exchange in the vehicle wireless communication system.Focusing on the design requirements of the radiation performances and anti-interference functions in the vehicle wireless communication system,in view of the design problems for suppressing the external signal interference and self-interference between array elements,this paper studies the optimization method of the anti-interference antenna-arrays with null controlling and sidelobe suppression and the optimization strategy of the Muiltiple-Input Muiltiple-Output(MIMO)antenna-arrays with the strip decoupling structure,respectively,and proposes the related optimization design of the symmetric curved-groove Defect Ground Structure(DGS)and the non-uniform strip-array Electromagnetic Band Gap(EBG)decoupling structure to improve the radiation performances and anti-interference ability of external signals and dense array elements.The main content and results are obtained as follows:(1)Optimization method of electronic control parameters for anti-interference antenna-arrays with null controlling and sidelobe suppression.Aiming at the design problems that various forms of nulls need to be controlled and sidelobe levels are too high in the antenna-array system interfered by external signals,the optimization method of electronic control parameters for the anti-interference antenna-arrays with null controlling at the specific positions and sidelobe suppression is firstly studied.The optimization model of null controlling at the specific positions and sidelobe suppression is established and the solution process is realized.The computational efficiency for solving the optimization problem gradient-based optimization algorithm is discussed.Then,the gradient-based optimization method with the specific null regions(single,single-width,double,multiple,annular null regions)and sidelobe suppression is proposed.The Kreisselmeier–Steinhauser(KS)function is used to describe the maximum value of the Peak Sidelobe Level(PSLL),and the constraints that satisfy the null depth in the specific regions are proposed.The sensitivity of the objective function with respect to the electronic control parameters is analytically deduced,and the optimization problem is efficiently solved based on the gradient optimization algorithm.Three typical design examples are given to illustrate the effectiveness of the proposed method.The proposed optimization method not only realizes the anti-interference ability in the specific positions and regions,but also significantly improves the radiation performances of the antenna-arrays.The KS function is introduced to describe the maximum value of the PSLL to ensure the differentiability of the objective function.The computational efficiency of the optimization problem can be greatly improved by the derived sensitivity information and gradient algorithm.(2)Optimization method considering mutual coupling for anti-interference antennaarrays via array layout and electronic control parameter.In order to further improve the radiation performances of the arrays while ensuring the precise null control,the optimization method considering mutual coupling for anti-interference antenna-arrays via array layout and electronic control parameter is proposed.The radiation characteristics to the element rotation direction are analyzed,and the rotation direction is introduced into the null controlling problem of excitation phase-only optimization at the specific positions for the collaborative design.The objection function is set to maximize the weight sum of the difference between the main-beam gain and the maximum value of the PSLL under the constraint of the null depth at the specific positions.The parameterized Method of Moments(Mo M)based on coordinate mapping is proposed to accurately calculate the radiation performances of the arrays.The sensitivities of the objective function to the element rotation direction and excitation phase are analytically derived,and the design examples of linear dipole and planar bowtie antenna-arrays are given to verify the effectiveness of the proposed method.Through collaboratively optimizing the rotation directions and excitation phases of array elements,the radiation performances can be further improved while ensuring the anti-interference ability of antenna-arrays.The parameterized Mo M based on coordinate mapping can strictly consider the mutual coupling effect between the elements and precisely control the positions of the nulls,while reducing the extra computational cost and avoid the re-mesh.(3)Shape optimization design of strip curved-groove decoupling structures for MIMO antenna-arrays.Aiming at the problems of serious mutual coupling effect,high correlation of each communication channel and poor isolation of antenna-arrays system subject to self-interference between array elements,the shape optimization design of the strip curvedgroove decoupling structures for the MIMO antenna-arrays is proposed.The shape description model of the curved-groove DGS is established and the decoupling mechanism is discussed.The curve shape function based on the trigonometric series is constructed,and the shape description parameters are extracted.The optimization strategy of strip-curved groove DGS is researched,and the new configuration of the MIMO antenna-array with the symmetric strip curved-groove DGS is designed.The experimental verification and performance analysis are given,and compared with the existing decoupling structures.The proposed stragety greatly improves the decoupling performances while guaranteeing the radiation performances of the MIMO antenna-arrays.The groove boundary of the curved groove DGS is well described by the curve shape function based on the trigonometric series expansion.The proposed design not only realizes the desired decoupling performance,but also ensures the radiation characteristics of the MIMO arrays,while reducing the correlation of the communication channels and improving the isolation between the array elements.(4)Optimization design of non-uniform strip-array EBG decoupling structures for MIMO antenna-arrays.In view of the advantages of EBG metamaterials in not destroying the original antenna structure and suppressing signal interference,in order to achieve the selfinterference suppression between the elements,the optimization design of the non-uniform strip-array EBG decoupling structure for the MIMO antenna-arrays in the Dedicated ShortRange Communication(DSRC)frequency band is proposed.The optimization strategy of the non-uniform strip decoupling structure is researched.The optimization model and the solution method of the decoupling structure are established,respectively.The new configuration of the array with the non-uniform strip-array EBG decoupling structure is designed.The experimental verification and performance analysis are given.The optimization strategy is extended to the millimeter-wave frequency band,and the optimization design of periodic non-uniform striparray decoupling structure based on the 77 GHz radar receiving antenna is proposed.The periodic decoupling structure is modelled,and the solution method is studied.The optimization process is summarized,and the performance comparisons are given.In the DSRC frequency band,the proposed design achieves the mutual coupling suppression and isolation improvement of the MIMO arrays,which reduces the self-interference between the elements.The proposed strategy is also suitable for the optimization design of periodic non-uniform strip-array decoupling structure in the 77 GHz millimeter-wave frequency band.On the basis of ensuring the array radiation performances,the surface wave distribution is adjusted and the decoupling performances between the radar receiving antenna elements are significantly improved. |
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