【作者】 王宁；

【导师】 刘运林；

【作者基本信息】 西南交通大学 ， 电磁场与微波技术， 2014， 硕士

【摘要】 天线作为无线电设备的关键部件,对通信系统的性能有着至关重要的影响。圆极化天线因为具有接收效率高及有效抑制雨雾干扰的特点,已在雷达、移动通信、电子干扰和卫星定位系统等领域中得到了广泛应用。本文通过结合相关科研项目,主要对圆极化天线的双频和宽带技术展开深入研究和探索,并在此基础上设计了一款双频圆极化微带贴片天线和两款宽带圆极化平面螺旋天线。文中首先介绍了近年来双频段和宽频带圆极化天线的研究现状,然后给出了微带天线的基本理论和实现双频、宽带圆极化的主要方法,接着分析了平面螺旋天线模型、工作原理和特性参数,最后是本文设计的三款圆极化天线,详细工作内容如下：设计了一款单馈电层叠式双频圆极化微带贴片天线,有效覆盖了北斗卫星导航系统(CNSS)的￡和S频段。天线采用层叠结构引入多谐振,并在贴片对角切角实现圆极化。通过引入空气层降低相对介电常数和在探针顶部加载容性金属片抵消了过长探针带来的感抗,实现了频段展宽。天线在数值仿真的基础上,获得较好的圆极化特性,结果表明,阻抗带宽在￡频段和S频段分别达到了82MHz和156MHz,3dB轴比带宽分别达到了18MHz和38MHz。本次设计不但实现了双频圆极化辐射,而且在每个频段的带宽都有所展宽,增加了天线在不同环境中使用的有效性与可靠性。最后完成了实物加工制作,并对回波损耗系数S11进行了测试与比较。设计了两款工作频率在1-12GHz的宽带圆极化平面螺旋天线。根据某项目要求,结合平面螺旋天线理论知识,首先对平面等角螺旋天线进行设计。为了实现平衡-非平衡间的转换以及天线输入阻抗与同轴线特性阻抗的变换,设计一种简单易加工的超宽带直线渐变型双面微带线巴伦。同时为了改善低频轴比,在螺旋臂末端加载吸收电阻,最终获得双向辐射的频比为12：1的宽带圆极化平面等角螺旋天线。鉴于项目对天线单向辐射的要求,后期进行了方案修改,设计了一款带有异形反射腔的阿基米德螺旋天线,并采用电性能更优的指数渐变结构微带巴伦对其馈电。最后利用电磁仿真软件进行分段仿真,对天线在每个频段的阻抗特性,主轴方向轴比特性,以及远场辐射方向图和增益等性能做出详细分析与讨论。结果表明,各项性能参数基本达到项目指标。更多还原

【Abstract】 As a key component of radio equipment, antenna has a critical influence on the performance of communication system. Because of high efficiency of receiving and effectively restraining the interference of rain and fog, the circularly polarized antenna is widely applied in the fields of radar, mobile communications, electronic interference and satellite positioning system and so on. The researches and explorations on dual-band and broadband technologies of circularly polarized (CP) antenna have done to the requirement of research projects. A dual-band CP microstrip patch antenna and two broadband CP spiral antenna are designed and optimized.Firstly, the recent research status of dual-band and broadband CP antenna is presented, then the basic theory of microstrip antenna and its main methods to achieve circular polarization are summarized. After that the planar spiral antenna is described, including the model, working principle and characteristic parameters. The final is about the design of three circularly polarized antenna. Details are as follows:A single-feed CP microstrip antenna is designed to covering L-band and S-band of beidou satellite navigation system (CNSS). Stacked patches with corner truncated are employed to get dual-band circular polarization. An air layer is applied to reduce the relative dielectric constant and a small capacitive metal piece is loaded to offset inductance, both methods are used to achieving a broad band. The results of numerical simulation show this antenna with good performance. In detail, the obtained impedance bandwidth in the L-band and S-band are about82MHz and156MHz, and CP bandwidths are about18MHz and38MHz. The antenna is not only with dual-band CP radiation, but also with bandwidth enhanced in each band. This increases the effectiveness and reliability in different environments. Finally, the antenna is manufactured and the measured result matched well with the simulated result.Two broadband CP planar spiral antenna with operating frequency in1-12GHZ are designed. According to project requirements and theoretical knowledge of planar spiral antenna, a planar equiangular spiral antenna is designed first. In order to achieve the conversion between equilibrium and non-equilibrium, as well as the transformation between the input impedance of antenna and the characteristic impedance of coaxial line, an easy processing ultra-wideband balun is designed, its structure is a trapezoidal double-sided microstrip line. At the same time, an absorbing resistor at the end of each spiral arms is loaded to improve axial ratio in low frequency. Finally, a broadband CP planar equiangular spiral antenna with dual radiations along axial direction is obtained successfully. According to one side radiation on antenna for the application environment, some changes are made later. An Archimedean spiral antenna with a shaped reflector cavity and a better exponentially gradient microstrip balun is designed. In view of ultra-wideband, segmented simulation are done by using electromagnetic simulation software. In the end, a detailed analysis and discussion are made, such as the input impedance, the axial ratio, the pattern and the gain. The results show that all the performance achieve the project targets.更多还原