Abstract
As described in this paper, we attempted real-time rainfall detection by analyzing the radiowave fluctuation of leaky coaxial cables (LCX), which are widely used in Japan as communications antennas. Because the radiowavefluctuation of communications antennas caused by rainfall is extremely slight and contaminated by noise, it is almost impossible to detect rainfall directly from that fluctuation. However, we specifically examined discontinuous changes of the signals caused by water droplets adhering to the antenna surface. Then we tried to evaluate the discontinuous characteristics at each signal point by a singularity, which is mathematical index. Using wavelet transform, we estimated the singularities of signal fluctuation measured outdoors. Comparison of the 1-min average of the singularities with the 1-min rainfall intensity revealed a difference in singularities between those occurring with rainfall and without rainfall. Statistical analysis revealed a time variation of singularities using Boxplot method. Results show a significant difference in the singularities of the signals obtained during rainfall to the distribution of the signals during no rainfall. Therefore, it might be possible to detect rainfall in real time by ascertaining differences in the singularities of the radiowave fluctuation of LCX.
