Magnetically coupled wireless communication for buried environmental sensor

Ambient sensors are finding their way into our lives and the world around us enabling a great deal of real time environmental monitoring applications. Solid medium, like soil, compost, ice and ore, with relatively high conductivity and non-uniform dielectric properties, provide a unique challenge. One particular case where this is acutely true is black schist ore. While opaque to the propagation of high frequency electric waves, frequencies in the kHz range, and magnetic fields, are better able to penetrate these medium. This paper describes transmission characteristics for this kind of ore. It continues to show the modeling and development of a simple, cheap and low power 125 kHz inductively coupled wireless communication system and demonstrates its performance at a black schist ore mine site.