为了保护应答器传输模块(BTM)天线不被线路上扬起的道砟损伤,以及尽量减少车底复杂电磁环境对BTM天线的干扰,在BTM天线四周加装钢材质的屏蔽板.通过仿真计算,分析屏蔽板取不同高度、距BTM天线不同水平距离时BTM天线的回波损耗以及与频率的关系,确定屏蔽板的高度为150mm,距BTM天线的水平距离为100mm.基于毕奥萨伐定理计算BTM天线的磁场强度,并仿真BTM天线磁场强度的分布以及对干扰信号的衰减.结果表明:加装屏蔽板后,不仅没有影响BTM天线的信号传输性能,还在一定程度上增加了天线的有效通信范围和对干扰信号的衰减,提高了接收信号的信干噪比,从而降低了误码率.对BTM天线加装屏蔽板的实车试运行结果也表明:所设计加装的屏蔽板,既能保护BTM天线,又能保证BTM天线正常的信号传输.%To protect the antenna unit of Balise Transmission Module (BTM) from being damaged by ballast and minimizing the interference of complex electromagnetic environment underneath the car on BTM antenna,steel shielding plates were installed around BTM antenna.Through theoretical calculation and computer simulation,the return loss of BTM antenna and the relationship between frequencies were analyzed under different heights of shielding plates and different horizontal distances from BTM antenna.The height of shielding plate was 150 mm,and the horizontal distance from BTM antenna was 100 mm.Based on the Biot Savart law,the magnetic field strength of BTM antenna was calculated,the distribution of the magnetic field intensity of BTM antenna and the attenuation of interference signal were simulated.Results show that the installation of shielding plates not only does not affect the signal transmission performance of BTM antenna,but also increases the effective communication range of the antenna and the attenuation of interference signal to a certain extent.The signal to noise ratio of the received signal is improved and the bit error rate is reduced.The results of the real vehicle test on BTM antenna with shielding plates also show that the shielding plates designed not only can protect BTM antenna,but also ensure the normal signal transmission of BTM antenna.
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