电离层调制加热产生极低频/甚低频波定向辐射的理论分析

通过低电离层调制加热能够产生极低频/甚低频(ELF/VLF)波. 基于调制加热理论, 并引入相控阵天线思想, 建立了通过双波束幅度调制模式(DAM)和圆形几何调制模式(CGM)产生ELF/VLF波的定向辐射模型, 并通过与实验数据的对比验证了模型的正确性. 据此模型, 采用HARRP加热阵参数, 对比分析了上述两种定向辐射模式与常规幅度调制模式(AM)之间的特性差异, 并研究了调制频率(f_ELF/VLF)和加热波束与垂直方向倾角(ψ)对各模式的影响. 结果表明: 相对AM模式, 通过合理设置初始相位、f_ELF/VLF和ψ, DAM 模式和CGM模式在实现ELF/VLF信号定向辐射的同时还可以提高其辐射强度, 相对AM模式, CGM模式信号强度最大提高约11.3 dB. 关键词： 定向辐射 双波束幅度调制 圆形几何调制

Theory of ELF/VLF wave directional radiation by modulated heating of ionosphere

ELF/VLF waves are generated via amplitude-modulated heating of the lower ionosphere. Based on the modulated heating theory, the directional radiation models of dual beam amplitude modulation (DAM) and circle geometric modulation (CGM) are established by introducing the phased array ideas, which are validated by comparison with the experimental data. According to the models, differences between the above two directional radiation models and the normal amplitude modulation (AM) are analyzed with parameters of HARRP phased-array HF facility, and the influences of the modulation frequency (f_ELF/VLF) and elevation of the heating waves on mode are investigated as well. Compared with the AM mode, DAM and CGM can realize the directional radiation, and enhance the radiant intensity by properly setting the initial phase, the modulation frequency (f_ELF/VLF) and angle of inclination of the heat wave to the vertical direction. The ELF/VLF radiant intensity may be increased by 11.3 dB when replacing AM with CGM.
Keywords： directional radiation dual beam amplitude modulation circle geometric modulation