| With the continuous development of electronic countermeasure technology and communication technology,radar plays a vital role in military detection,the Internet of Things,and autonomous driving.As a radar cross-section enhancement structure,the retrodirective array has the capability of electromagnetic wave auto-tracing.Due to its low cost,lightweight,and planar characteristics,it has attracted widespread attention from scholars both domestically and internationally in recent years and has been applied in radar targets,long-distance RFID tags,and autonomous driving beacons.However,the large size of the feeding network for the retrodirective array leads to increased structural scattering,not only reducing the effect of backward radar cross-section enhancement but also making it difficult to meet the requirements for highly integrated applications of the retrodirective array.Therefore,this dissertation focuses on the complex structures of the retrodirective arrays,the large size of the feeding networks,and the low integration level,researching compact retrodirective arrays design methods.Moreover,addressing the current shortcomings of the retrodirective arrays,such as short coverage distance,limited scanning dimension,and single working band,research on1-D/2-D retrodirective arrays in modular,larger scale,and dual-frequency directions has been conducted.The main research contents and innovative achievements of this dissertation are summarized as follows:Study on compact modular 1-D retrodirective arrays: Addressing the problem of complex feeding networks and limited coverage distance of the dual-frequency 1-D Van Atta retrodirective array,a compact dual-frequency 1-D Van Atta retrodirective array design method is proposed.This method uses structural reuse technology to effectively reduce the number of input ports for the dual-frequency antenna array,thus reducing the complexity and size of the feeding network.The dual-frequency 1-D Van Atta retrodirective array designed based on this method has a compact structure and can increase the radar cross-section through modular application to enhance backward distance.Additionally,by theoretically studying the scattering field composition of the R-KR lens retrodirective array and analyzing the main reasons affecting the monostatic radar cross-section flatness and working bandwidth,a modular structure of double R-KR lenses is proposed.This structure overcomes the problems of limited working bandwidth and poor monostatic radar cross-section flatness of the single R-KR lens retrodirective array,which increases the relative working bandwidth by about 13% and reduces the maximum fluctuation of monostatic radar cross-section at the center frequency from 14 d B to 3 d B.Study on compact 2-D broadband retrodirective array: Addressing the issues of low integration,large volume,high cost,and weight of larger-scale 2-D Van Atta retrodirective arrays,a planar miniaturization design method is proposed.This method integrates the structures of the broadband planar feeding network and the broadband planar antenna array,using the same layer of air medium to achieve the design of dual-layer phase-constant transmission line and broadband antenna.Within a limited array aperture,a broadband planar miniaturized feeding network consisting of 32equal-length transmission lines was successfully realized.The size of the 2-D 8×8 Van Atta retrodirective array designed based on this method is 4.67λ×4.67λ×0.105λ,with the advantages of compact structure,low cost,low weight,and high integration.Compared with the similar-scale researches,it can enhance the backward radar cross-section within a broadband range of 8.9 GHz ～10.4 GHz under the premise of a planar structure.Study on compact 2-D dual-frequency retrodirective array: A design method for the compact dual-frequency 2-D Van Atta retrodirective array is proposed,including a low-complexity dual-frequency feeding network and frequency-reconfigurable artificial magnetic conductor antenna miniaturization technology.By reducing the input ports of the dual-frequency 2-D antenna array,this method effectively reduces the complexity of the dual-frequency feeding network and reduces its size.By using structure reuse and frequency selection technology,a 100% structure reuse rate of the frequency-reconfigurable artificial magnetic conductor antenna is achieved,realizing the miniaturization of the antenna.The size of the compact dual-frequency 2-D Van Atta retrodirective array designed based on this method is 2.98λ×2.98λ×0.068λ,with the structural advantages of low profile,planarization,and high integration,capable of achieving 5.8 GHz and 11.4 GHz dual-frequency as well as 2-D backward radar cross-section enhancement.Based on the compact dual-frequency Yagi antenna for 1-D/2-D retrodirective arrays: Firstly,a design method for a compact single-port dual-frequency Yagi antenna is proposed,utilizing various frequency selection technologies such as the parallel LC structure,the spatial filter,and the frequency-selective surface.The designed dual-frequency Yagi antenna comprises dual-frequency exciter,reflectors,director,and beam-tilting structure,featuring a compact structure,tunable frequencies,and adjustable dual-frequency gains.Furthermore,combining the design methods of compact dual-frequency retrodirective arrays,dual-frequency 1-D end-fire,slant,and 2-D end-fire retrodirective arrays were designed.Secondly,addressing the complexity and weight issues of the feeding network for the dual-frequency 2-D end-fire Van Atta retrodirective array,a design method using planar structure transmission lines to form the end-fire type dual-frequency 2-D retrodirective array feeding network is proposed.This method restructures the three-dimensional,cross-dimensional,cross-plane feeding network into multiple cascaded planar feeding networks,reducing design difficulty and complexity.Compared to feeding networks composed of coaxial cables,the designed feeding network has the advantages of being compact,lightweight,and low-cost. |
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