Foliage obstacle detection exploiting scattering and depolarization of 2.4 GHz waves used for communication links

In this paper, a new method for foliage obstacle detection is presented using the scattering and depolarization of the transmitted waves, used for the communication of wireless sensors, located on power cable towers. The communication nodes use the 2.4 GHz IEEE 802.15.4 protocol and they form a fire alert sensor network. Foliage in the line of sight or even or even the Fresnel zone of the communication nodes cause scattering and depolarization of the incident wave. This depolarization can be detected by the strictly linearly polarized antennas of the communication sensors, through the degradation of the received signal quality. Consistent degradation implies the existence of growing foliage that can potentially cause fire. The sensing and detection of foliage in the proximity of power cables creates an alarm signal for further action. This paper demonstrates that foliage dielectric properties, in realistic size and shape can cause significant depolarization of the 2.4 GHz linearly polarized waves used for the nodes communication, thus enabling the foliage detection.