Through applying a 4-MHz linear frequency modulation waveform, which has high range resolution and signal intensity, we successfully detected for the first time the ionospheric 150-km echo enhancement at 430–450 MHz of the Ultra-High-Frequency (UHF) band using the newly built Sanya Incoherent Scatter Radar (SYISR). The obtained low signal enhancement (less than 0.5 dB) explains why previous UHF experiments did not detect them. We also found that our measured fine structure shows a much wider forbidden region than previous results and covers a much larger altitudinal and local time region. In comparison with recent upper-hybrid instability theory and simulation, our results confirmed the predicted higher altitude occurrence, wider gaps between enhancements, the turn corner feature around sunrise, and perhaps the weak enhancement, which provide an independent evaluation of the newly proposed mechanism in UHF band. Future UHF experiments could further improve the physical understanding of 150-km echo phenomenon.

中文翻译：

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在 UHF 频段首次探测到神秘的低纬度 150 公里回波


通过应用具有高距离分辨率和信号强度的 4 MHz 线性频率调制波形，我们首次使用新建的三亚非相干散射雷达 （SYISR） 成功探测到超高频 （UHF） 频段 430-450 MHz 的电离层 150 公里回波增强。获得的低信号增强（小于 0.5 dB）解释了为什么以前的 UHF 实验没有检测到它们。我们还发现，我们测量的精细结构显示出比以前的结果更宽的禁区，并且覆盖的海拔和当地时间区域要大得多。与最近的高空混合不稳定理论和模拟相比，我们的结果证实了预测的更高的高度出现、增强之间的更宽的间隙、日出周围的转弯特征，以及可能的弱增强，这为新提出的 UHF 频段机制提供了独立评估。未来的 UHF 实验可以进一步提高对 150 km 回波现象的物理理解。