【作者】 江椿；

【导师】 焦永昌；

【作者基本信息】 西安电子科技大学 ， 电磁场与微波技术， 2011， 硕士

【摘要】 天线是移动通信系统的关键硬件设备之一。随着移动通信的飞速发展,系统的复杂度越来越高,不断升级的通信系统希望有效解决多径衰落问题,减少天线数量,降低天线和选址的成本,而双频双极化基站天线能够很好地满足这些要求。因此研究双频双极化基站天线十分必要,且具有理论意义和实用价值。论文主要研究并排式和共轴式两种不同实现方案的双频双极化基站天线。通过不同的方案,对所设计的双频双极化基站天线工作频带内的驻波比、隔离度、辐射方向图等进行比较研究。论文的主要工作概括为以下几个方面:1、设计了不同的双极化高隔离度宽频带基站天线单元。双频双极化基站天线同时工作在CDMA/GSM900频段(824MHz-960MHz)和DCS1800/3G频段(1710MHz-2170MHz)。对并排式双频双极化基站天线,文中设计了两种振子:压铸模对称振子和印刷对称振子,每种振子包括工作在不同频段的两个单元。共轴式方案中,设计了一种具有双频特性的组合振子,DCS1800/3G频段采用L型探针耦合馈电的十字交叉印刷振子,低频段采用T型探针耦合馈电的双层环状金属片作为辐射单元,两者相互嵌套,具有相同的相位中心。另外对一种L型探针馈电的双频圆形贴片振子进行了仿真。2、根据不同的方案,设计了双频双极化天线阵列。首先确定天线单元的间距,选择适当的天线反射板形状和尺寸。对并排式方案,分析了不同频段阵列的列间间距对阵列方向图的影响,寻找出最优的间距尺寸。对共轴式双频双极化天线阵列,分析了耦合对天线的影响。通过两种方案天线的加工和测试,比较了不同方案下双频双极化基站天线阵的驻波比、隔离度、辐射方向图等特性,并分析了两种方式下基站天线性能的优劣性。3、研究了基站天线方向图波束综合赋形方法。根据基站天线在实际应用中的需要,采用遗传算法对阵列方向图进行了赋形设计,对天线垂直面方向图第一上旁瓣、第一下零点、主瓣下倾角等指标进行了优化。针对传统阵列综合中忽略阵元互耦导致优化结果不精确的问题,该方法提取了仿真软件考虑单元互耦和阵列环境对单元影响后的单元方向图,将其纳入优化过程,提高了计算结果的准确性。更多还原

【Abstract】 Antenna is one of key components in the mobile communication system. Therapidly development of mobile communications makes the system become more andmore complex. In order to meet the upgrade requirements, we need to effectively solvethe multi-path fading problem, decrease the number of antennas, and reduce the cost ofantennas and site selection. The dual-frequency dual-polarized base-station antennas canbe used to follow these requirements. Therefore, it is extremely necessary to make astudy on this kind of antennas, which is of theoretical and practical values.In this thesis, two different schemes, i.e. abreast and coaxial dual-frequencydual-polarized base-station antennas are studied. Comparison of the VSWRs, theisolations, and the radiation patterns for these two dual-frequency dual-polarizedbase-station antennas has been made. The main contributions of this thesis aresummarized as follows:1. Different dual-polarized base-station antenna elements with high isolation aredesigned. Dual-frequency dual-polarized base-station antenna operates simultaneouslyboth the CDMA/GSM900 (824-960MHz) and the DCS1800/3G (1710-2170MHz)bands. For the abreast dual-frequency/dual-polarized base-station antennas, two types ofdipoles are designed: compression mold and printing dipoles, each with elementsoperating in different frequency bands. In the coaxial scheme, a dual-bandcombined-dipole is devised. In the DCS1800/3G band, we adopt cross printing dipolefed by L-probes. While in the lower frequency band, we use circular metal layers fed byT-probes as its radiation unit. The two portions are nested within each other, and havethe same phase center. In addition, a dual-frequency double-deck rounded patch elementfed by L-probes is simulated.2. Two dual-frequency dual-polarized antenna arrays according to the abreast andcoaxial schemes are designed. First, we determine the antenna element spacings, andselect the appropriate reflector. For the abreast scheme, we analyze the column spacingsbetween arrays with different bands and find out the optimal size. While for the coaxialdual-frequency dual-polarized antenna array, we focus on the effect of element couplingon antenna performance. These two antenna arrays have been fabricated and measured.Their VSWRs, isolations, and radiation patterns are compared. Both the advantages anddisadvantages of the base-station antenna performance in these two cases are alsodiscussed. 3. The base-station arrays with shaped-beam pattern are synthesized. Accordingthe need in practical applications, genetic algorithm for shaping array patternsadopted to optimize the vertical antenna pattern, such as first upper side lobesuppression, first lower zero filling and electrical down-tilt. Aiming at the inaccuracythe optimized results caused by ignoring mutual coupling among array elementstraditional array synthesis, the element patterns calculated by the simulated software,which the mutual coupling and effect of array environment on the elements areconsidered, are used in the process of optimization, to improve the synthesis accuracy.更多还原