主字母体制调制系数的选择

Selection of Modulation Index of High Alphabet Systems

针对靶场安全控制系统主字母体制中主字母信号的调制系数选取范围问题,对主字母信号经FM(Frequency Modulation,调频)调制后的功率进行理论分析,选取一组频率组成主字母信号调制到中频。通过仿真得到数据曲线。同时将仿真参数移植到与工程设备相似的实验设备上,使用频谱仪进行实际测试,以测试数据拟合出曲线,该曲线符合理论分析及仿真曲线,即理论分析、仿真与设备测试结果一致。可以得出结论,在主字母体制信号可解调的条件下,调制系数与主字母信号经FM调制后的功率的关系函数为对数函数,从而可为工程参数的选择提供参考范围,有利于工程应用。

To determine the suited range of modulation index in high alphabet systems for range safety control,the power of high alphabet FM（Frequency Modulation）is theoretically analyzed and high alphabet signals composed of a set of frequencies are modulated to intermediate frequency.A curve of high alphabet FM power and modulation index is got through program simulation.The simulation parameters are transplanted into experiment equipment similar to engineering equipment and a test is performed with a spectrum analyzer and a fitting curve is got from test data.The curve is good agreement with theoretic analysis,i.e.theoretic analysis,simulation and equipment test results are consistent with each other.As long as signals of the high alphabet system can be demodulated,relationship of the useful modulation index and high alphabet FM power can be expressed in a logarithm function and this avails a range for selection of engineering parameters for project application.