Research And Design Of Shared Aperture Antennas Based On The Characteristic Mode Analysis

The development of wireless information technology puts forward higher requirements for the communication systems.And the multi-function and integration become the trend of communication systems,which poses higher challenges to antenna design.In this case,the shared aperture antenna has significant advantages and broad application prospects for solving the needs of communication systems such as multi-frequency band,multi-polarization,multi-beam and integration.This thesis systematically summarizes the research status of shared aperture antennas,and proposed some innovative methods.In terms of the key technical difficulties faced in design process,such as low-profile,high-gain,broadband,multi-frequency band,multi-polarization and scanning enhanced of antenna array,etc.Based on the characteristic mode theory,starting from the basic radiation principle of the antenna,some innovative ideas and technologies are proposed.The organization of the dissertation can be summarized as follows:(1)In view of requirements of antennas such as multi-frequency band,multi-polarization,low-profile and high gain,etc.A unidirectional low-profile dual frequency dual polarized shared-aperture bowtie antenna are studied and designed.Firstly,a basic dipole antenna is designed based on characteristic mode analysis;two modified bowtie type antennas are nested inside the basic bowtie patch on the same PCB board,which extremely contributes to the compactness of the antenna.However,the coplanar arrangement of octave-separated bands makes it challenging to design just one reflector.So,an artificial magnetic conductor(AMC)reflector has been applied to shared-aperture bowtie antenna to achieve high-gain unidirectional radiation performance.The proposed antenna has stable gain in each of working frequency band;it has certain engineering application value and lays the foundation for a more complex dual-frequency dual-polarization shared-aperture antennas.(2)According to the broadband and multi-polarization demands,a novel broadband dual circularly polarized(CP)array based on metasurface structures is proposed.Four rotated metasurface elements fed with 90° phase difference are employed in this design,and crossed L-shaped probes are used to achieve dual CP operation for each element.The working mechanism of the proposed metasurface antenna element is investigated by using characteristic mode analysis(CMA).Measured results show that the propose antenna has a wide operation bandwidth of 44.4% and peak gain of 8.8 d Bic.Compared with others,the proposed one has obvious advantages in bandwidth and polarization diversity.(3)To meet the demands of wide-angle scanning array work applications.According to the characteristic mode analysis,a scanning enhanced low-profile broadband phased array is proposed by introducing the radiator-sharing approach to the metasurface which consists of E-shaped cells.The antenna array is excited by L-probe feed.What's more,two adjacent antenna array elements share one columns of the patches,resulting in compact size of the array with only 10 columns of E-shaped patch cells.Due to there is no spacing between the radiating elements,the radiator-shared antenna array exhibits maximum scan angles of ±60°,which has good engineering application value.(4)For multi-polarization scanning array requirements,based on the proposed dual CP metasurface antenna,a shared-aperture dual circular polarization scanning array is put forward.The designed array antenna has a simple and compact structure and has a scan angle in the range of ±30°.In addition,the left/right circular polarization axis ratio of the array is below 3-d B during the scanning process,which maintains good circular polarization characteristics and has certain application prospects.