| Wireless communication technology,with its advantages of flexible application,real-time performance,high efficiency and extensive coverage,is widely used in 5G communi-cation,satellite communication,radar detection,smart home and many other fields.How-ever,with the increasing diversification and complexity of application scenarios and user requirements,wireless communication systems are facing increasingly severe challenges in terms of size,weight,and performance,which gradually gave birth to the concept of shared-aperture antennas and arrays.Compared to traditional antenna systems,shared-aperture systems allow multiple antennas and arrays with different operating frequencies and polarization to work normally within the same aperture,exhibiting unique advantages in system integration.Shared-aperture technologies offers a new direction for the devel-opment of wireless communication,but also introduces a series of new research problems and challenges.On the one hand,for shared-aperture systems with multiple frequencies,the compact physical structure can easily cause strong cross-band interference and block-ing among the subsystems,thus affecting their matching and radiation performances and even damage the overall efficiency and communication quality of the wireless communi-cation system.On the other hand,for shared-aperture systems with multiple polarization,the mutual interference between different polarization may also affect system performance.Especially,for circular polarization favored by long-distance communication,its unique chiral rotation property introduces a certain degree of coherence between the left-and right-handed circularly polarized(LHCP and RHCP)phases,thus limiting the application flexibility and potential of dual-circularly-polarized(dual-CP)systems.Furthermore,with the increase of operating bands and polarization of shared-aperture systems,the complex-ity of internal architecture and feeding network also elevates significantly,making it more difficult to achieve good frequency and polarization isolation.Therefore,the integration of antennas and arrays across multiple bands and polarization has been a long-standing research focus and technical challenge for shared-aperture antennas and arrays.In re-sponse to the above problems and challenges,this dissertation takes the multi-frequency shared-aperture array antenna as the research object,and conducts detailed discussions and studies from antenna level and array level around the frequency and polarization iso-lation problems in shared-aperture systems,specifically focusing on three key issues in shared-aperture technology:cross-band interference suppression,decoupling of dual circular polarization,and multi-frequency multi-polarization array integration.The main research contents and contributions of this dissertation include the following aspects:1.Focusing on the problem of cross-band interference in shared-aperture antenna systems,research around the space filtering technology based on electromagnetic meta-surface is conducted.The low-frequency 5G antenna is placed above the high-frequency Wi Fi antenna to improve the spatial utilization of the shared-aperture construction.Then,in response to the blocking effect introduced by this layout,a compact 5G/Wi Fi shared-aperture antenna with normal radiation is designed based on a single-layer electromagnetic metasurface with frequency-selective characteristics,achieving±45~°polarization in the5G band and vertical polarization in the Wi Fi band,with relative bandwidth of 23.7%and 2.8%,respectively,and half-power beam width(HPBW)of over±30~°.Further,by extending the rectangular layout of the metasurface to a honeycomb layout,a 5G/Wi Fi shared-aperture antenna with conically omnidirectional radiation is designed,achieving dual polarization in the 5G band and vertical polarization in the Wi Fi band,with relative bandwidth of 9.5%and 4.7%,respectively,and omnidirectional HPBW of over±25~°.The two shared-aperture antennas achieve cross-band cooperative working,multi-polarization,and high gain,providing methodological support for applications such as indoor 5G/Wi Fi communication,blind compensation and signal conversion.2.Focusing on the problem of chiral coupling between the dual-CP phases in shared-aperture array antennas,research around the decoupling modulation of dual circular polar-ization is conducted.The simple-structured and lightweight air-fed reflectarray is adopted to achieve low-cost control on dual circular polarization.Then,based on the circularly-polarized phase modulation mechanisms of the reflectarray units,a polarization-decoupled dual-CP shared-aperture reflectarray antenna with fixed beam directions is designed based on an anisotropic unit,achieving decoupled beams of(120~°,10~°)and(135~°,-30~°)under LHCP and RHCP excitation,respectively,with relative bandwidth of 19.4%and 11.4%,and aperture efficiency of 29.3%and 22.8%.Further,a dual-motion full-metal reflectarray unit is proposed,based on which a reconfigurable polarization-decoupled dual-CP shared-aperture reflectarray antenna is designed.The 1×1-bit dual-CP phase compensation is achieved through simple mechanical control of the unit’s four states,and thereby realizing decoupled dual-CP 2-D beam scanning of±50~°,with aperture efficiency of 20.9%,provid-ing methodological support for achieving independent control over dual-CP 2D scanning.Literature investigation demonstrates that this is the first time that the polarization decou-pling and 2-D beam steering of dual circular polarization are achieved simultaneously.3.Focusing on the challenge of multi-frequency multi-polarization array integra-tion in shared-aperture array systems,research around multi-frequency multi-polarization shared-aperture array antenna is conducted.The shared-aperture form of’reflectarray+phased array’is adopted to balanced the size,cost,and gain requirements of the shared-aperture array system.Then,a broadband and highly selective spatial filtering structure is designed based on a dual-periodic electromagnetic metasurface,utilizing a stacked shared-aperture construction of the K-band array with the Ku-band and X-band arrays.Further,based on the spatial filtering structure,polarization-decoupled dual-CP operations with fixed beam directions are separately achieved for the Ku-band and K-band dual-CP re-flectarrays.Then,the shared-aperture construction between the Ku-band and X-band arrays is accomplished using the structure reuse technique,and dual-linearly-polarized(dual-LP)2-D beam steering is achieved for the X-band array.Specifically,at 24 GHz,the shared-aperture array antenna achieves decoupled beam directions of(45~°,-30~°)and(135~°,-30~°)under LHCP and RHCP excitation,respectively?at 14 GHz,it achieves decoupled beam directions of(45~°,30~°)and(135~°,30~°)under LHCP and RHCP exci-tation,respectively?at 10 GHz,the shared-aperture array antenna achieves dual-LP 2-D beam scanning of±45~°.This design provides a feasible solution for multi-band multi-polarization shared-aperture array integration. |
