| With the arrival of the interconnection of all things,the fifth generation(5G)wireless communication system has become the most important new infrastructure for social development.People's demand for mobile communication continues to increase,and the requirements for signal transmission speed and quality are higher.5G has become the focus of high-tech competition in the world.With a variety of broad-band wireless access technologies becoming mature,various wireless technologies upgrading,the rapid development of Internet of things technology,wireless mobile communication has entered a new stage of social development and integration.All these indicate that 5G,the Internet of Things,autopilot,telemedicine,artificial intelligence and other applications in civil and military fields are more and more.The data volume of these systems is growing at an exponential rate,and the demand for channel capacity and signal transmission reliability is increasing rapidly.However,due to the limited spectrum resources,in order to make more efficient use of the limited spectrum resources in the complex noise environment,multiple antennas must be arranged in the restricted space.At the same time,higher requirements are submitted for the coupling between antennas and the correlation between signals.MIMO antenna system can effectively improve the channel capacity and reliability,and is an important device in a wireless communication system.In this context,this paper focuses on the research of 5G terminal MIMO antenna and miniaturization design based on metamaterials.(1)The design and theoretical analysis of 5G dual-band MIMO high isolation antenna based on EBG structure of electromagnetic band gap are proposed.The first resonance mode is generated by loading parasitic rectangular patch under the meander-line part of antenna,and the meander-line realizes the second resonance mode,so as to achieve 5G double frequency operation.In order to achieve high isolation at both resonant modes.Firstly,the band gap characteristics of EBG structure are used to realize decoupling in the second resonant mode.Secondly,four openings are loaded at the junction of the upper surface elements of EBG structure to realize decoupling in the first resonant mode.In this paper,the dispersion characteristics and reflection phase characteristics of EBG are discussed and analyzed,and then a high isolation MIMO antenna based on the electromagnetic band gap is proposed.This design solves the multi frequency decoupling problem and directional enhancement problem of MIMO antenna.The research results were published in IEEE Transactions on antennas and promotion,an international academic journal,by SCI the first author.(2)An isolated and enhanced MIMO antenna array based on the split miniaturized EBG structure is proposed.The using of EBG to reduce coupling usually involves larger structures in size and volume,and these materials are not particularly attractive when ease of implementation and miniaturization become key issues.In regard of this situation,we provide a new compact EBG structure.At the same time,it is proposed that the isolation enhancement can be realized by applying an opening gap on the original EBG surface.Finally,the isolation degree at the working frequency is more than 50 dB.The first applicant applied for a patent for related research results.(3)MIMO monopole antenna based on ultra-fine transmission line(TL)structure is proposed.By loading an ultra-fine transmission line resonator on one side of the antenna unit,its function is equivalent to reflector and parasitic elements,which effectively achieves high isolation and bandwidth expansion.The source of coupling in MIMO antenna and the working mechanism of ultra-fine transmission line as a parasitic element and reflector are studied.In addition,a kind of orthogonal polarization diversity four element antennas based on ultra-fine transmission line is proposed.Finally,the results of simulation are verified by manufacture and measurement of the antennas.The decoupling structure used in this work has a good prospect for MIMO antenna application in the future.Compared with EBG structure or other decoupling structure,it has strong practicability and is easy to be integrated with other RF circuit.The research results were submitted AEU International Journal of electronics and communications with SCI academic paper,as the first author.(4)The design of high isolation and high efficiency multi-via patch antenna array based on TL structure is proposed.In this paper,the parameters and the design concept of multi-via patch antenna are studied.Compared with the multi-via patch antenna array without TL structure,the isolation between antennas is increased by 17 dB with TL structure.The isolation design improves the radiation gain and efficiency of the multi-via patch antenna.The isolation improvement mechanism and design process of multi hole patch antenna are analyzed in detail,and the physical processing and experimental verification are carried out.It is verified that the ultra-fine transmission line TL structure is not only suitable for the decoupling of multi-element monopole MIMO antenna,but also effective for the decoupling of patch-like multi-antenna.(5)A compact and low-profile patch MIMO antenna based on a novel parallel coupled transmission line is proposed.The decoupling structure is composed of four staggered parallel ultra-fine transmission lines(4TL),and the decoupling of the low-profile patch antenna array with a complete common ground plane is realized.The 4TL structure forms a high impedance surface,which hinders the propagation of surface wave and realizes the high isolation design of MIMO patch antenna.This paper analyzes the working principle and parameter changes of 4TL in detail.The design of MIMO patch antenna in this paper provides a good solution for the high isolation design of complete common ground plane patch antenna array,which has the advantages of simple fabrication and easy design.This design different from the previous designs that need to etch grooves or make modification on the ground plane,the radiation characteristics of the antenna will not be affected.Finally,the antenna array with and without 4TL is fabricated and measured to verify the simulation results.(6)A miniaturized dual-branch broadband antenna based on a novel ultra-wideband one-dimensional EBG structure with slow-wave factor is proposed.The novel one-dimensional EBG structure unit cell is composed of a slot etched diagonally around the rectangular patch.Through this design,the slow wave bandwidth is significantly improved,the miniaturization of double branch broadband antenna is realized.In addition,the bandwidth of the dual-branch antenna is extended due to the phase reflection characteristics of the one-dimensional slow wave EBG structure.The EBG structure is embedded in the middle of the double branch antenna and the ground plane.The analysis is carried out in two cases of loaded and unloaded EBG structure.Finally,the miniaturized antenna and un-miniaturized antenna are fabricated and tested.The results show that the test results are basically consistent with the simulation results,which verifies that the new EBG structure with high slow-wave factor can effectively reduce the size of the dual branch monopole antenna. |
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