| Nowadays,with the rapid development of millimeter wave technology,many practical applications,such as 5G communication,satellite communication,and short distance wireless transmission,have put forward higher requirements for communication rates.For the millimeter wave band with rich spectrum resources,it is an effective solution to achieve a higher communication rate by improving the working bandwidth of the communication system.As the transceiver of the communication system,the antenna plays a decisive role in the overall working bandwidth of the system.With the increase of frequency band,the transmission loss also increases,which makes the antenna array with directional high gain become the first choice in millimeter wave communication.In increasingly complex communication environments,circularly polarized antennas have the advantage of being insensitive to polarization and reducing multipath effects.Therefore,the circularly polarized antenna can provide a more stable communication link for the communication system.This dissertation focuses on the research of broadband millimeter-wave planar circularly polarized antenna arrays,and designs competitive antenna arrays for different application scenarios.The specific research work is as follows:(1)Based on the circular polarization principle of folded long dipoles,an ultra-wideband circularly polarized antenna structure with dipoles loaded spiral branches is proposed.Combined with the wide-band characteristics of slot coupling feed,the corresponding ultra-wideband circularly polarized antenna array is designed by means of microstrip feed.The operating bandwidth of the antenna array covers the whole Ka-band,and it has great application potential in both 5G millimeter wave communication and satellite communication.(2)A broadband circularly polarized antenna element based on an asymmetric slotted rectangular patch is designed.Then,the antenna element is expanded to 4 × 4 and 8 × 8 scale antenna array using the microstrip feed network.The measured results show that the proposed antenna array achieves a wide bandwidth in Q band.The designed 8 × 8 array finally achieved a circular polarization bandwidth of 32.75～49.3GHz(40.1%).In addition,the antenna array has the advantages of low profile,high efficiency,small size,and direct integration with RF front-end system,so it can be well applied to various communication systems working in Q band.(3)Based on the circular polarization mechanism of parallel magnetic dipoles and electric dipoles,a broadband circular polarization magnetoelectric dipole antenna element is proposed.The antenna element consists of a magnetic dipole consisting of a coupling slot and a pair metal pole and an electric dipole consisting of a dual-mode dipole.Due to the electric field vectors of the magnetic dipole and the electric dipole of the proposed antenna element being orthogonal in space and having a 90 ° phase difference,the circularly polarized radiation characteristics are realized.Considering the asymmetry of its structure size,when assembling arrays,sequential rotation is adopted to ensure that the overall axial ratio performance of the array does not deteriorate,and on the other hand,the overall size of the array is reduced by making the elements more compact.Finally,a 2 × 2 broadband magnetoelectric dipole circularly polarized antenna array is designed.The designed 2 × 2 antenna array achieves 40.17%(35.8～53.8GHz)circularly polarized operating bandwidth.(4)A single-layer Archimedes spiral antenna structure with a gradually wider arm width is proposed.Compared with the stacked spiral antenna,the proposed antenna has the advantages of a simple structure and low processing cost.Subsequently,the antenna element is composed of 8 × 8scale antenna array.Finally,the antenna array achieves 45.9%(29～46.3GHz)circularly polarized bandwidth. |
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