下一代无线通信系统终端电磁超材料天线及MIMO系统研究

发布时间：2018-10-11 13:16

【摘要】：随着第四代移动通信时代的到来,移动通信系统的需求越来越趋于更大容量、更高数据传输速率和更好的服务质量。一方面4G通信覆盖频带进一步展宽,无线终端天线的发展方向越来越趋于宽频带、多频带和高性能,而预留给天线的空间却越来越小,天线设计的小型化问题变得尤为重要。另一方面采用多输入和多输出(MIMO)的通信系统能够提高通信容量和信道传输可靠性,势必成为最有前景的宽带无线通信发展方向之一。对于体积有限的无线终端设备来说,在狭小的空间内放置多个天线,并确保各天线的独立有效工作,是目前无线终端MIMO天线技术面临的巨大挑战。本文通过引入超材料的设计思想,研究基于复合左右手传输线零阶谐振的小型化天线设计、高隔离度MIMO天线设计以及加载电阻性吸波材料的终端天线降SAR问题,以实现手机天线的多频带、小型化、高性能等。文章首先介绍了超材料的基础理论,包括左手材料的原理以及其独特的电磁特性,推导了左手材料中的电磁传播特性。接着分析了复合左右手传输线(CRLH-TLs)及其等效电路模型,详细介绍了复合左右手传输线的实现、应用和零阶谐振特性;同时重点介绍了MIMO技术的基本原理和天线比吸收率SAR的定义和标准,介绍了终端设备SAR值测试的基本环境。其次设计了一款覆盖LTE频段的新型智能手机终端天线。通过应用零阶谐振原理在天线设计中加载等效左手电容、左手电感结构和引入地回路电流的方法,实现了天线的小型化、高性能设计。该天线频带覆盖LTE747/GSM850/900/DCS1800/PCS1900/UMTS/LTE2300/2600,具有较好的辐射特性,较高的辐射效率和增益,能够满足LTE智能移动终端的设计要求。文中对该天线的工作特性给出了详细分析,同时进行了加工测量,实测结果显示加工的天线与仿真结果吻合,该零阶谐振天线具有小型化和高性能的优点。接下来文章介绍了几种MIMO天线的去耦方法,能够提高天线单元间的隔离度。以一款零阶谐振天线为单元,构造四单元MIMO天线系统,讨论四种不同摆放位置情况下天线单元之间的耦合情况。选取两种放置方式,通过加载中和线和缺陷地结构两种不同的方法,提高天线单元间的隔离度。最后给出了一款双零阶手机天线模型,以该模型为基础,通过一组以不同方式加载电阻性表面材料的结果对比,验证了这种电阻性材料的加载能够损耗掉天线向人头方向辐射的功率,减小天线SAR值。同时通过分析周期型的R-Cards和加载FSS频率选择表面的R-Cards两种模型,保证降低天线SAR值的同时,确保天线的辐射效率,实现更好的性能表现。
[Abstract]:With the arrival of the fourth generation mobile communication era, the demand of mobile communication system tends to be more and more large capacity, higher data transmission rate and better quality of service. On the one hand, the coverage band of 4G communication is further broadened, the development direction of wireless terminal antenna tends to be more and more wide band, multi-band and high performance, but the space reserved for antenna becomes smaller and smaller, so the miniaturization of antenna design becomes more and more important. On the other hand, the multi-input and multi-output (MIMO) communication system can improve the communication capacity and channel transmission reliability, which is bound to become one of the most promising broadband wireless communication development direction. For wireless terminal devices with limited size, it is a great challenge for wireless terminal MIMO antenna technology to place multiple antennas in a narrow space and ensure the independent and effective operation of each antenna. In this paper, the design of miniaturized antenna based on zero-order resonance of composite left-right hand transmission line, the design of high isolation MIMO antenna and the SAR reduction problem of terminal antenna loaded with resistive absorbing material are studied by introducing the design idea of supermaterial. In order to achieve the mobile phone antenna multi-band, miniaturization, high performance and so on. This paper first introduces the basic theory of metamaterials, including the principle of left-handed materials and its unique electromagnetic properties, and deduces the electromagnetic propagation characteristics in left-handed materials. Then, the CRLH-TLs and its equivalent circuit model are analyzed, and the realization, application and zero-order resonance characteristics of the compound left-right transmission line are introduced in detail. At the same time, the basic principle of MIMO technology and the definition and standard of antenna specific absorptivity SAR are introduced, and the basic environment of terminal equipment SAR testing is also introduced. Secondly, a new smart phone terminal antenna covering LTE band is designed. By applying the zero-order resonance principle to the antenna design, the equivalent left-handed capacitance, the left-handed inductance structure and the introduction of the earth loop current are applied to realize the antenna miniaturization and high performance design. This antenna has better radiation characteristics, higher radiation efficiency and gain, and can meet the design requirements of LTE intelligent mobile terminal. In this paper, the working characteristics of the antenna are analyzed in detail, and the machining measurements are carried out. The measured results show that the fabricated antenna is in good agreement with the simulation results. The zero-order resonant antenna has the advantages of miniaturization and high performance. Then, several decoupling methods of MIMO antenna are introduced, which can improve the isolation between antenna elements. Using a zero-order resonant antenna as a unit, a four-element MIMO antenna system is constructed, and the coupling between the antenna elements in four different positions is discussed. Two placement methods are selected to improve the isolation between antenna elements by two different methods: load neutralization line and defective ground structure. Finally, a dual-zero-order antenna model of mobile phone is presented. Based on the model, the results of a group of resistive surface materials loaded in different ways are compared. It is verified that the loading of the resistive material can reduce the radiation power of the antenna toward the human head and reduce the SAR value of the antenna. At the same time, the periodic R-Cards model and the R-Cards model loaded on the FSS frequency selective surface are analyzed to ensure that the SAR value of the antenna is reduced, and the radiation efficiency of the antenna is ensured, and better performance is achieved.
【学位授予单位】：西安电子科技大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TN828.6

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