Research On The Theory And Technology Of Wide-Angle Beam Scanning Array Antenna

In the era of the Internet of Everything,to support the diverse needs of wireless systems for building a multi-dimensional integrated system for land,sea,and air,the beam scanning antenna array,as the “eyes” of wireless systems,plays a significant role in enhancing the system’s stability and coverage.On the one hand,on highly mobile carriers such as aircraft,warships,and vessels,beam scanning antenna arrays with wide-angle beam coverage capability are crucial for expanding the target tracking range.On the other hand,to meet the demands for higher data rates,higher resolution,greater signal-to-noise ratio,and improved sensitivity in wireless systems,the scale and operating frequency of beam scanning antenna arrays are on the rise,leading to increased power consumption and challenges related to the size of transmit-receive component modules and the element spacing of non-grating arrays.Existing research on wide-angle beam scanning antenna arrays faces many challenges,such as limited scanning range for 2D planar antenna arrays,low side lobe level performance in wide-angle scanning,and low array efficiency.Spherical conformal antenna arrays suffer from high profiles,and it’s difficult to generate wide-angle beams with asymmetric conformal aperture radiations.Existing sub-arrayed antenna array designs are complex,have low engineering feasibility,and lack designs for special arrays like circularly polarized subarrays and conformal subarray antenna arrays.To address the above challenges,this dissertation starts from the principle of synthesizing the array pattern of beam-scanning antenna arrays.It focuses on a series of theoretical and technical research related to wide-angle beam scanning antenna arrays including adjusting the element pattern,modifying the array factor(element positions),and adjusting the subarray array factor(subarray combinations).The main work and achievements of this dissertation are summarized as follows:1.To achieve high efficiency two-dimensional wide-angle scanning for beamscanning antenna arrays,this dissertation proposes a high-efficiency mechanoelectrical hybrid scanning antenna array,starting with the adjustment of the element pattern.Unlike existing mechanoelectrical scanning antenna arrays that rotate horizontally,the proposed array only rotates in the elevation plane with only three fixed rotation states,allowing for faster beam switching speeds.To achieve high-gain and wide-angle two-dimensional scanning performance for the array,a corresponding array model was established,and the optimal element pattern and mechanical rotation angles were designed.As a result,the antenna array achieved a scanning range of ±67° in the yoz plane and ±75° in the xoz plane,improving the worst sidelobe level by 3 d B compared to existing research and increasing the efficiency from around 45% in existing research to 75%.2.Addressing the limitation of existing hemispherical conformal antenna arrays with large beam coverage but high profiles that restrict their usage scenarios,by adjusting the positions of the elements in the hemispherical conformal antenna array and modifying the original array’s factor,this dissertation introduces a novel low-profile wide-angle scanning concave sector-cut conformal antenna array structure.Based on the proposed low-profile conformal array topology,a distributed virtual aperture synthesis method is further presented,allowing elements in discrete region space to synthesize relatively consistent radiation apertures during the scanning process to ensure improved scanning performance with reduced profile.Simultaneously,by appropriately designing the array’s profile height and element’s 3 d B beam-width,the impact of blockage is minimized.In the end,this antenna,with a 43% reduction in profile compared to the original hemispherical conformal antenna,achieves scanning performance that is essentially consistent within the hemispherical beam coverage range.3.To address the issues of limited difference patterns range in existing antenna arrays and the challenges associated with extending the difference patterns generation range using conformal antenna arrays,such as the problem of low zero-depth in the difference patterns due to asymmetric radiation apertures and poor main lobe symmetry,this dissertation presents a difference patterns synthesis model based on an iterative convex optimization method.This model first utilizes a multidimensional vector clustering method to generate the initial difference pattern for the asymmetric three-dimensional conformal antenna array,thus determining the constraints on the main lobe and sidelobes of the difference pattern.Furthermore,by introducing an auxiliary phase function,it transforms the non-convex constraint on the symmetry of the main lobe of the difference pattern into a convex constraint.Finally,the optimal difference pattern is obtained through iterative convex optimization.Both numerical and full-wave simulation results demonstrate that the proposed method can generate highly symmetric wide-angle difference pattern with sidelobes below-20 d B and zero-depth differences exceeding-42 d B for hemispherical conformal antenna arrays at θ = 75° and conical conformal antenna arrays at θ = 45° with asymmetric radiation apertures.Additionally,the generation range of difference patterns is improved by more than 66.7% compared to existing work4.To address the issues of deteriorating axial ratio and poor engineering feasibility when using existing subarray methods for circularly polarized subarray design,this dissertation presents a a subarray approach for planar circularly polarized wide-angle beam-scanning antenna arrays.In the proposed method,a modified two-dimensional entropy model is introduced to enforce constraints on the arrangement of dual-grid subarrays,resulting in a modular layout of subarrays with alternating horizontal and vertical positioning.This layout,in turn,incorporates subarray-level rotation feeding to improve the array’s axial ratio.Due to the relatively regular arrangement of subarray feeding networks in the proposed layout,it exhibits higher engineering feasibility.Furthermore,to suppress sidelobe levels during array scanning while maximizing the array gain,a convex optimization synthesis method based on the subarray layout is investigated.Numerical and simulation examples are provided for comparison.The final step involves designing a real circularly polarized element and validation arrays for experimental verification.The test results for the validation array demonstrate that the arrays have a low axial ratio(less than 1.2 d B)at the center frequency for θ = 0° and θ =45°.With the same circularly polarized elements,the array’s 3 d B axial ratio scanning range is increased from 20°,as in existing subarray methods,to 45°,achieving circularly polarized low axial ratio for wide-angle beam scanning.Additionally,the results indicate that the subarray approach proposed in this dissertation has the potential to support broadband circular polarization operation for subarray antenna arrays.5.To further expand the beam scanning range of subarray circularly polarized antennas and address the challenge of low-cost,low-complexity design for large-scale,high-gain spherical conformal beam-scanning antenna arrays,this dissertation introduces a subarray approach for spherical conformal circularly polarized wide-angle beamscanning antenna arrays.By introducing the concept of three-dimensional space entropy for spherical conformal antenna arrays,the article divides the two-element subarrays for different scanning angles on the spherical antenna aperture into a unified subarray partition,avoiding issues related to variations in radiation aperture.Furthermore,using the maximum three-dimensional space entropy model,the article identifies optimal combinations of subarray forms for different elements,resulting in an optimal subarray layout topology and establishing a comprehensive model for the desired target polarization pattern.To validate the model’s effectiveness,numerical simulation results for subarray conformal antenna arrays of different scales are provided.The results show that within the half-space beam coverage range,the optimal subarray-based array,with only half of the T/R channels,exhibits a directivity only 1.1 d B to 1.9 d B lower than the original array.Additionally,when compared to other conventional arrays with the same number of channels,the optimal subarray-based array demonstrates excellent scanning performance.