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小型化高隔离度MIMO天线的研究与设计
Research and Design of Miniaturized and High Isolation MIMO Antennas
【作者】 王晨；
【导师】 洪劲松；
【作者基本信息】 电子科技大学 ， 无线电物理， 2018， 硕士
【摘要】 无线通信飞速发展的现今,人们对通信系统也有着越来越高的要求,比如通讯系统的带宽、信道容量和传输速率等等。在输入端和输出端都使用了多根天线的MIMO通信系统可以利用多径效应来有效的提高系统的通讯效率。作为MIMO通信系统核心之一的MIMO天线是影响MIMO系统性能的关键。随着无线通讯终端的发展,天线尺寸也越发趋于小型化。如何在缩小尺寸的情况下,保持MIMO天线中天线单元的高隔离度是MIMO天线研究的重点。本文从UWB-MIMO天线的方向图分集和极化分集入手设计了三款天线:第一款是二元方向图分集特性的UWB-MIMO天线。该天线印制在厚度为1.6mm,尺寸为36*36mm~2,相对介电常数为4.4的FR4介质基板上。天线的阻抗带宽为3.1-11.7GHz,在工作频带上天线的隔离度都大于15dB甚至能达到50dB以上。天线采用了两个背对放置的半椭圆天线单元,通过“E面对称切除法”来实现天线的小型化和方向图分集的特性,另外还在天线地板上使用了背对放置的类F型地板枝节来提高天线的隔离度使之满足MIMO天线设计的要求。第二款是二元极化分集特性的UWB-MIMO天线。该天线尺寸为30*30mm~2,印制在厚度为0.8mm,相对介电常数为4.4的介质基板上。天线的阻抗带宽为2.84-11.16GHz,天线的隔离度大于15dB而且在大部分频带上都大于20dB。天线使用了正交放置的天线单元来实现天线的高隔离度和天线的极化分集特性。再在天线单元周围添加地板枝节,利用天线单元与周围地板枝节的电流耦合来改善天线的阻抗匹配。最后得到的天线尺寸足够小,结构简单,方法也比较新颖。第三款是四元极化分集的UWB-MIMO天线。该天线大小为48*48*0.8mm~3,使用的是相对介电常数为4.4的FR4介质基板。天线的阻抗带宽为3.60-11.57GHz,在工作频带上天线的隔离度都大于15dB。该天线利用第二款天线的方法由第二款天线演变而来,同样利用了天线单元与地板枝节的电流耦合来扩宽阻抗带宽。该四元天线结构新颖简单,尺寸也较小。
【Abstract】 With the rapid development of wireless communications,people have higher and higher requirements for communication systems,such as the bandwidth,channel capacity,and transmission rate of communication system.A MIMO communication system using multiple antennas at the input and output ends can effectively improve the communication efficiency of the system by utilizing multipath effects.MIMO antenna,which is one of the core of MIMO communication system,is the key to affect the performance of MIMO system.With the development of wireless communication terminals,the antenna size has also become more and more compact.How to maintain the high isolation of the antenna elements in the MIMO antenna in the case of downsizing is the focus of the MIMO antenna research.In this thesis,three antennas are designed based on the directional pattern diversity and polarization diversity of UWB-MIMO antennas:The first is a two-element UWB-MIMO antenna with pattern diversity.The antenna was printed on an FR4 dielectric substrate with a thickness of 1.6 mm and a dielectric constant of 4.4.The impedance bandwidth of the antenna is 3.1-11.7 GHz,and the antenna isolation in the operating frequency band is greater than 15 dB and can reach more than 50 d B.The antenna uses two half-ellipse antenna units placed opposite to each other,and the"E-plane symmetry cutting-off method"is used to realize the miniaturization of the antenna and the characteristics of the pattern diversity.In addition,on the antenna floor,back-to-back F-shaped floor joints are used to improve antenna isolation to meet the MIMO antenna design requirements.The second type is a two-element UWB-MIMO antenna with polarization diversity.The antenna size is30*30mm~2,printed on a dielectric substrate with a thickness of 0.8mm and a dielectric constant of 4.4.The impedance bandwidth of the antenna is2.84-11.16GHz.The antenna isolation is greater than 15dB and is greater than 20dB in most frequency bands.The antenna uses orthogonally placed antenna elements to achieve high antenna isolation and antenna polarization diversity characteristics.Then,a ground node is added around the antenna unit,and the impedance matching of the antenna is improved by the galvanic coupling of the antenna unit and the surrounding floor nodes.The resulting antenna size is small enough,the structure is simple,and the method is relatively novel.The third type is a four-element UWB-MIMO antenna with polarization diversity.The antenna size is48*48*0.8mm~3,using an FR4 dielectric substrate with a dielectric constant of 4.4.The impedance bandwidth of the antenna is 3.60 to 1.57 GHz,and the antenna isolation in the operating frequency band is greater than 15 dB.The antenna is evolved from the second antenna using the method of the second antenna.It also uses the galvanic coupling of the antenna element and the ground stub to widen the impedance bandwidth.The four-element antenna has a novel and simple structure and a small size.