超表面圆极化天线

发布时间：2018-01-05 00:22

本文关键词：超表面圆极化天线　出处：《西南交通大学》2017年硕士论文　论文类型：学位论文

【摘要】：随着无线射频技术的进步,线极化天线已经不适用于的特殊的设备要求。在远距离传输和抗干扰方面,圆极化天线有显著的优势,圆极化波在雨雪中传播衰减小,能穿透电离层,不受地球磁场产生的法拉第效应(Faraday effect)影响。圆极化天线在无线通信领域应用十分广泛,比如全球定位系统(GPS,Global Position System),RFID阅读器天线,电子不停车收费(ETC,Electronic Toll Collection)系统天线。圆极化天线还被广泛应用在雷达监测如云雨天气监测,日常林火监测,海洋浮游生物监测,水位检测。本文先对天线的发展和超材料发展的国内外现状进行介绍分析,还介绍了天线的基本参数和超材料的基本种类。再对微带天线圆极化的不同技术路线进行了介绍和分析,对单馈法圆极化天线的圆极化理论和腔模理论进行了推导,了解几何微扰对简并模产生的影响。接着,研究超表面产生圆极化的原理,设计了 5.8GHz缝隙天线和超表面。该超表面由4*4个周期性单元构成,是在正方形的金属表面进行不规则开槽设计,其作用相当于一个有圆极化功能的空间滤波器。加载超表面后可以把缝隙天线的线极化波转变为圆极化波,缝隙天线的阻抗带宽(S11-10dB)为5.70-5.96GHz,加载超表面后圆极化波的轴比带宽为5.03-6.22GHz,增益达6dB,该超表面还可以屏蔽工作频带外的电磁干扰。然而,由于该超表面面积尺寸太大,不适用于对小型化程度要求很高的阅读器天线,所以对超表面的小型化方法进行了研究。缝隙天线的结构不变,超表面仅为以前超表面的1/16大小,但超表面的加载方式发生了改变,需要紧密贴合在微带缝隙贴片天线背面。加载后的阻抗带宽(S11-10dB)为5.65-6.05GHz,缝隙天线的原始轴比为60dB,加载一层超表面后轴比降为1OdB,加载两层超表面后轴比最低降为5dB,加载三层超表面后轴比降为小于3dB,轴比带宽为5.52-5.64GHz。可见,增加多层超表面后,天线的轴比带宽可以得到扩展,轴比也会降低。另外,因为FR4的厚度增加,等效介电常数增加,所以中心频率有所降低。最后,研究了超表面旋转角度对极化状态的影响,缝隙天线的结构不变,尺寸有所调整,阻抗带宽(S11-10dB)为5.53-5.90GHz。当超表面和缝隙天线对齐时,可以实现左旋圆极化,轴比带宽为5.74-5.85GHz,当超表面旋转90度时,可以实现右旋圆极化,轴比带宽为5.78-5.94GHz。圆极化天线的体积仅为25mm*25mm*4mm。极化状态实现的原理是不同角度的超表面会产生不同的阻抗相位差,+90°的相位差和-90°相位差产生不同状态的圆极化波,圆极化旋转方向相反。
[Abstract]:With the development of wireless RF technology, special equipment of linear polarization antenna is not suitable to the requirements in the long-distance transmission and anti interference, circular polarization antenna has advantages, circular polarized wave attenuation propagation in the rain and snow, can penetrate the ionosphere, is not affected by the earth's magnetic field generated by the Faraday effect (Faraday effect) effect. Circular polarized antenna is widely used in the field of wireless communications, such as the global positioning system (GPS Global, Position System), RFID reader antenna, electronic toll collection (ETC, Electronic Toll Collection) system. The antenna circular polarized antenna is widely used in radar monitoring such as rain weather monitoring, daily monitoring of forest fire monitoring, marine plankton the water level detection, are introduced in this paper. First the development of antenna and metamaterial development situation at home and abroad, also introduces the basic parameters of the antenna and ultra basic materials Class. Then different technical route of microstrip antenna with circular polarization are introduced and analyzed, the single feed circularly polarized antenna with circular polarization theory and the theory of cavity are deduced, to understand the effect of geometrical perturbation for degenerate mode generated. Then, the principle of circular polarization study of ultra surface, design the 5.8GHz slot antenna and super surface. The super surface is composed of a 4*4 periodic unit is irregular slotted design on the metal surface of the square, which is equivalent to a circular polarization function of the spatial filter. Loading surface can get the slot antenna line polarization wave into circular polarization wave impedance bandwidth gap the antenna (S11-10dB) for 5.70-5.96GHz, after loading over the surface circular polarization axial ratio bandwidth is 5.03-6.22GHz, the gain of 6dB, the surface can also shield the work band electromagnetic interference. However, due to the high surface area size Too big, do not apply to requirements for the reader antenna miniaturization degree is very high, so the miniaturization method of the surface. The same slot antenna structure, super surface is only the surface of the 1/16 before the super size changed but super surface loading, need to be tightly abutted on the back side of the microstrip slot the patch antenna impedance bandwidth. After loading (S11-10dB) for 5.65-6.05GHz, the original axis of the slot antenna is 60dB, add a layer of super surface of rear axle ratio dropped to 1OdB, loading the two layer over the surface than the minimum rear axle is reduced to 5dB, loading the three layer of super surface rear axle ratio decreased to less than 3dB, the axial ratio bandwidth of 5.52-5.64GHz. visible increase, multilayer super surface, axial ratio bandwidth of the antenna can be extended, the axial ratio will be reduced. In addition, because the FR4 thickness increases, increase the equivalent dielectric constant, so the center frequency is reduced. Finally, the super surface rotation angle Effect on the polarization state of the invariant structure of slot antenna, size adjustment, impedance bandwidth (S11-10dB) is 5.53-5.90GHz. when the super surface and slot antenna alignment, can realize left-handed circular polarization axial ratio bandwidth is 5.74-5.85GHz, when rotated 90 degrees over the surface, can realize the right-hand circular polarization, axial ratio bandwidth of 5.78-5.94GHz. circle polarized antenna volume is only the principle of 25mm*25mm*4mm. polarization is achieved over the surface of different angles have different impedance phase difference, phase difference and +90 DEG -90 DEG phase difference circular polarized wave generated in different states, circular polarization rotating in the opposite direction.

【学位授予单位】：西南交通大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TN821.1

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