天线的选择 Antenna Selection
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| 天线的选型 在移动通信网络中，天线的选择是主要的一部分，应根据网络的覆盖要求、话务量、干扰和网络服务质量等实际情况来选择天线。天线选择得当，可以增大覆盖面积，减小干扰，改善服务质量。由于天线的选型是与覆盖要求紧密相关的，根据地形和话务量的分布要求可以把天线使用的环境分为城区、郊区、农村和公路四种类型。 1、 天线使用中存在的问题 (毕业设计) （1） 较少考虑实际的地形与天线方向图的关系，而仅仅考虑覆盖的话务量分布来选择天线。比如在全向天线的选择方面，全网都使用同一种型号的全向天线，天线高低较高时，由于垂直面波束很窄，造成“塔下黑”的现象。 （2） 在使用天线时，如果机械倾角很大，方向图就畸变，造成覆盖或干扰的问题。仿真表明，真对不同增益的天线，应该有不同的下倾角限制要求。 （3） 过于追求天线的高增益性能，而忽略了高增益天线的一下缺点。导致几乎全网使用的天线增益都很高，高增益天线的缺点表现为体积大、重量大、副瓣高、零瓣深和垂直面波束窄。 Antenna Selection The antenna selection is a very important part in a mobile communication network. The antenna must be selected according to the actual conditions, such as coverage requirement, traffic volume, interference, and the quality of service of the network. A proper antenna can enlarge coverage area, reduce interference, and improve the quality of service. Because antenna selection is closely related to coverage requirement, the antenna application environment can be divided into four types according to landforms or traffic distribution. They are: urban area, suburban area, rural area, and highroad. 1、 Problems Present in Antenna Selection This section introduces the problem present in antenna application from the following perspectives: The antenna is selected only based on the covered traffic distribution, but little consideration is given to the relationship between landforms and antenna directional diagram. For example, if all antennas used in a network are of the same type, when the antenna is installed at a high position, the phenomenon of "blind under tower” will be present because the width of the beams in vertical plane is narrow. |