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基于EBG结构的新型PIFA天线研究
Study of New PIFA Antenna Based on EBG Structure
【作者】 王菲；
【导师】 李龙；
【作者基本信息】 西安电子科技大学 ， 电磁场与微波技术， 2010， 硕士
【摘要】 移动通信和个人无线通信技术的快速发展,使得通信系统对应用于其终端的天线提出了新的要求：一方面要求天线的小型化、宽频带和多频化；另一方面要求天线辐射对人体的影响降到最低。平面倒F天线(Planar Inverted-F Antenna, PIFA)因其具有体积小、重量轻、剖面低、可内置、易于加工、且易于和载体共形等突出的结构特点以及能实现宽频带和多频段的特性而得到了广泛的应用。新型电磁材料的研究及其应用越来越受到人们的关注。微波光子晶体,也称为电磁带隙结构(Electromagnetic Band-Gap, EBG)或者电磁晶体,是一种具有频率禁带的新型周期结构,可以有效控制电磁波的传播,其特有的性质使得电磁晶体具有广泛的应用前景。本文以EBG结构和PIFA天线基本理论为基础,采用电磁仿真软件结合实验测试,对EBG结构的小型化进行了研究,并将其应用到PIFA天线中,同时设计了一个宽频带和一个多频段PIFA天线。本论文的主要工作及创新之处如下：1.基于EBG结构的工作原理和频率特性,采用交指型结构增大EBG等效电容的方法,设计了一种小型化的EBG结构。直接传输法仿真得到该交指型EBG结构的带隙范围为2.2-2.SGHz。相对于常规的矩形EBG结构,结构周期长度减小为二分之一,面积减小为四分之一,小型化因子为50%。2.从PIFA天线的结构研究入手,介绍了PIFA天线的主要性能参数和基本分析方法。对微带天线的小型化、宽频带和多频带技术进行了分析与总结。在此基础上,研究并设计了一种双L型缝隙加载三频PIFA天线,该天线工作在GSM(0.89～0.96GHz)、DCS(1.71～1.88GHz)和ISM(2.4～2.484GHz)三个频段。此外,利用地板开槽技术,设计了一种新型宽频PIFA天线。该天线工作频率范围为2.3～6.3GHz(S11≤-10dB),相对带宽达到93%。研究并总结了这两个天线结构参数对天线性能的影响,并制作了天线进行测试,测试结果与仿真结果吻合较好。3.研究EBG加载前后,手机PIFA天线的人脑比吸收率SAR(Specific Absorption Rate)值。将设计好的小型化交指EBG结构应用于手机PIFA天线。研究表明,加载EBG结构的新型PIFA天线,人脑比吸收率有所降低,同时提高了天线的增益和效率。实际制作了天线并进行了SAR测试,测试结果与仿真结果吻合良好。
【Abstract】 With the rapid development of mobile and personal wireless communication technologies, the new requirements for antennas used to communication terminals have been proposed:On one side the antennas are required to be miniaturized, broadband, and multiband; On the other side we should minimize the influence of antenna radiation on human body. Planar inverted-F antenna (PIFA) coming out during these years has been rapidly and widely adopted because it has the structural advantages of small size, light weight, low profile, internally equipped, easily fabricated and mounted on the carrier. A PIFA has the properties of broadband and mufti-band.The research and application of new electromagnetic material are more and more concerned. Microwave photonic crystals, also referred an electromagnetic bandgap (EBG) materials, are periodic structures characterized by the existence of frequency band gaps, which has a great of applications in the future because of its new properties. Based on the basic principles of the PIFA antenna and EBG structures, the miniaturization of EBG structure and the application of EBG structures to PIFA are studied by using electromagnetic simulations and experiments. Furthermore, a broadband PIFA antenna and a mufti-band PIFA antenna are designed.The main work and achievements of this thesis can be summarized as follows:1. The operating principle and frequency characteristics of the EBG structures are discussed. By means of interdigitating structure to increase the equivalent capacitance, a new kind of miniaturized EBG structure is designed. Utilizing direct transmission method, we get the surface wave bandgap of the interdigitating EBG structures is 2.2-2.8GHz. Compared to the conventional rectangular EBG structures, the proposed EBG structure reduces the length of half and the area of one quarter. The miniaturization factor is about 50%.2. A detailed description on the configurations of PIFA antennas and the principal characteristics and analysis methods are introduced. Meanwhile, the miniaturized, broadband and mufti-band technologies about the microstrip antenna are analyzed and summarized. Based on this, a new triple-band PIFA with dual-L-shaped slot-loaded is proposed and studied, which can operate at GSM (0.89～0.96 GHz)、DCS (1.71～1.88 GHz) and ISM (2.4～2.484GHz). In addition, by means of cutting slots on the ground plane suitably, a new kind of broadband PIFA was designed. The antenna operated at frequency range from 2.3GHz to 6.3GHz (S11≤-lOdB), with relative bandwidth up to 93%. The relationship between antenna parameters and performance of antennas are analyzed and discussed. The two new PIFA antennas have been fabricated to conduct experiments. The measurement results are in good agreement with simulation results.3. The interdigitating EBG structure is applied to the PIFA in mobile handset. The performance and the specific absorption rate (SAR) of new PIFA with EBG structures were analyze and compared with a conventional PIFA in the same environment. The results show that the PIFA integrated with EBG structures can reduce the SAR and improve the antenna gain and efficiency. Finally, the new PIFA with EBG structures was fabricated and the SAR was measured by using DASY5 system. The measured results agree well with the simulated results.