ETC系统中路侧单元下行链路的频谱特性研究

Study on Spectrum Characteristics of the Road Side Unit Downlinks in ETC System

文章介绍了一种采用ADS软件数据流仿真获得射频电路频谱特性的方法,并采用该方法对ETC系统中路侧单元下行链路的频谱特性进行了分析,详细讨论了影响输出信号带外杂散电平的因素,给出了满足国标频谱模板的射频电路合理设计方法即中频调制法,通过解调信号与原信号对比一致性验证了该方法的正确性。该方法虽然稍微增加了射频电路的硬件成本,但给出的射频电路性能指标优异,可有效降低杂散发射电平及对临近信道的干扰,并且工程易实现。

In this paper a mathod to acquire spectrum characteristics of RF circuits using Data Flow controller of ADS software was introduced. With this method the spectrum characteristics of road side unit downlinks in ETC system were analyzed, followed by a detailed discussion on affecting factors of spurious level. Then a reasonable solution of RF circuits named IF Modulation Method to meet spectrum mask in National Standard was present. The correctness of the method is verified by contrasting with the baseband signal after demodulation and the original signal. Although the hardware cost of the RF circuits is increased a little in this method, but the RF cicuits has excellent performance with very low spurious level and can be easily implemented.