| With the rapid development of modern wireless communication technology and the rapid increase of wireless communication demand in different application scenarios,such as radio broadcasting,mobile communication,satellite communication,satellite positioning and other wireless systems have been widely used in vehicle wireless systems.The traditional implementation of vehicle wireless system is to provide independent wireless system for each system,in which the antenna of each system is also independent.This antenna layout will undoubtedly increase the design cost and is not conducive to the miniaturization of the system.It is urgent to develop high-performing and miniaturized vehicle antennas that can meet the requirements of different wireless systems at the same time.In this paper,the research work is carried out under the background of this demand.Due to the different demand of each wireless system in the vehicle,the antenna satisfying each wireless system also has the index requirements of different frequency,different polarizations and different radiation directions.In view of this,the innovative research on dual-band microstrip antennas with different polarizations and radiation properties is carried out for three specific application scenarios: GPS,satellite communication and 5G mobile communication.Finally,three novel antennas are designed to meet the above three application scenarios.The specific research work can be summarized as follows:1.A dual-band microstrip antenna with different polarizations and radiation properties based on the patch resonator: Firstly,the field distribution and radiation characteristics of square patch antenna and circular patch antenna at various resonance modes are studied,and the design methods of antennas with directional circular polarization and omnidirectional linear polarization are summarized.Then the circular-polarization directional antenna and the linear-polarization omnidirectional antenna are combined organically to design a dual-band microstrip antenna with different polarizations and radiation properties.The center frequencies of the designed antenna are 1.575 GHz in the low frequency band and 3.5 GHz in the high frequency band.The radiation characteristics of unidirectional right-handed circular polarization and omnidirectional linear polarization are realized in two bands respectively.In addition,the antenna also has the characteristic of low profile.These properties can meet the needs of GPS and 5G mobile communication.2.Design of a dual-band microstrip antenna with different polarizations and radiation properties and good frequency selectivity: In order to further improve the frequency selectivity of the designed antenna,based on the thorough analysis of the coupling characteristics between radiation elements of patch antenna,this paper designs a dual-band microstrip antenna with different polarizations and radiation properties with good frequency selectivity by introducing a cascaded high-low impedance microstrip structure into the feed network and changing the feeding scheme.According to this,the central frequencies of the two bands of the antenna are 1.575 GHz and 3.5 GHz,respectively and the directional radiation of right-handed circular polarization and omnidirectional radiation of linear polarization are realized.Theoretical and experimental results show that the antenna has no other harmonics in the frequency range of 0.5 GHz to 7.5 GHz,together with good frequency selectivity.In addition,the isolation between the two ports is also increased from - 8 dB to - 35 dB.The improvement of these characteristics can readily meet the needs of GPS and 5G mobile communication.3.Design of a dual-band antenna with different polarizations and radiation properties and high gains: In order to further improve the gain in the two bands,based on the thorough analysis of the coupling characteristics between the radiation units of the patch antenna,by changing the laminated structure of the planar printed circuit board form(PCB)to the pure metal structure and changing the feeding scheme,a dual-band antenna with different polarizations and radiation properties with high gain characteristics is designed in this paper.In this context,the central frequencies of the two bands of the antenna are 2.5 GHz and 3.5 GHz,respectively and the directional radiation of right-handed circular polarization and the omnidirectional radiation of linear polarization are realized.Theoretical and simulated results show that the gain of the antenna increases from 6 dBic and 4.5 dBi to 9.8 dBic and 7.6 dBi,respectively with a significant increase of more than 3 dB.The improvement of this characteristic can better meet the requirements of vehicle satellite communication and 5G mobile communication. |
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