| In the past few decades,a number of standards appears with rapid development of wireless mobile communication.In order to meet the requirements of these services,an increasing number of antennas are required in the communication systems to cover as many frequency bands as possible.Recently,multiband and coplanar multiple antenna integrated techniques have emerged to reduce the antenna size,improve the integration level of the systems while decreasing the cost at the same time.In this dissertation,several coplanar integrated multiple antenna systems for mobile station and terminals are proposed based on independent structure combination,partial structure composite and theory of characteristic modes(TCM)-based whole structure composite techniques.Traditional problems of multiple antenna systems such as high profile,low isolation,large size in the integrated coplanar multiple antenna systems are solved.The researches in this dissertation can be concluded as three parts:1.The method based on conventional independent structure combination is used to solve traditional problems of multiple antenna systems,such as high profile and low integration level.Firstly,due to the defect of high profile brought by conventional methods and the demands of conventional outdoor base stations,suspended patch is utilized to replace dipole to realize low frequency unit.A dual-band,dual-polarized antenna unit and an antenna array based on this unit are proposed.The profile of this base station antenna array is reduced to nearly half of the conventional one while other performances are guaranteed.Secondly,a planar integrated four-antenna system for mobile tablet terminals is proposed for Mobile Ad-Hoc networks(MANET),satellite navigation and satellite communication services in sub-urban mobile terminals.Two identical printed monopoles fed by coplanar waveguide(CPW)are applied to achieve transmitting and receiving MANET antennas.Satellite navigation and satellite communication antennas are realized by the two horizontal dipoles with parasitic metal strips on the back side.Simulated and measured results show that the two MANET antennas can realize omnidirectional radiation in horizontal plane from 316 to 708 MHz,which can meet the transmitting and receiving requirements of the MANET service.Meanwhile,the satellite navigation and satellite communication antennas can generate the broadside patterns covering the whole upper space.Compared with conventional three-dimension structures,the proposed planar antennas are easier to be integrated into the mobile tablet terminals and reduce the size and weight of the terminals.2.Based on the concept of planar integrated multiple antenna design with partial structure composite technique,two structure-shared integrated planar antennas are developed using cavity slot and patch.Firstly,specific modes of the rectangular patch and rectangular cavity are chosen and excited according to the mode analyses.Matching cavity and matching patch are introduced to improve the impedance matching of the cavity slot antenna.A broadside triport multiple-input and multiple-output(MIMO)antenna with isolation higher than 18 dB is achieved,which can be applied in 5G massive MIMO communication systems to reduce the dimensions of the massive MIMO antenna array.Secondly,a planar integrated antenna operating at 5.8 and 28 GHz is developed based on the modal analyses of the cavity and patch,as the circular cavity working in millimeter wave band is taken as circular patch radiating in low frequency.These researches can provide important theory basic and technical support for the design of the miniaturized and integrated antennas applied in millimeter wave communication systems.3.Based on the concept of planar integrated multiple antenna design using whole structure composite technique,two miniaturized wideband planar integrated antennas are proposed.Firstly,two characteristic modes(CMs)with monopole-like patterns and lowest resonant frequencies are chosen according to the characteristic mode analysis(CMA)of a shorting circular patch.A dual-mode monopole-like patch antenna with high bandwidthto-volume ratio is developed.Secondly,to satisfy the requirement of the indoor MIMO communication,a different method of loading shorting vias and slots is utilized to adjust the modal patterns and frequencies.A triport MIMO antenna is achieved using a single patch.The planar triport antenna has properties of wide bandwidth,high isolation and low profile due to two orthogonal modes at each port.The performances of this antenna are verified by the simulated and experimental results.The researches in this part provide technical basis for the miniaturization of indoor base station antennas.4.Based on whole structure composite technique,two high-isolation wideband and ultra-wideband(UWB)MIMO antennas based on printed monopole loaded with tapered slot are proposed to resolve the low-isolation issue of UWB MIMO antennas in mobile terminal platforms.Firstly,the characteristics of the modal currents on the printed monopole loaded with back-to-back tapered slot are analyzed using CMA.A high-isolation two-port UWB MIMO antenna is realized by exciting two mode types.Secondly,another novel printed monopole loaded with tapered slot in its top middle part is developed.A real planar high-isolation UWB MIMO antenna with upper space fully covered is realized.It has a common ground for two ports with the introduction of an integrated CPW-slot transmission line.Three methods of realizing coplanar integrated multiple antenna systems are introduced in this dissertation.Several miniaturized low-profile coplanar integrated multiple antenna systems for mobile communication systems are developed.These researches provide theoretical basis and technical support for multiband and multiple antenna coplanar integration techniques in the future. |
PDF Full Text Request