Employing a metamaterial inspired small antenna for sensing and transceiving data in an underground soil sensor equipped with a GUI for end-user

A methodology to extract sensor data from underground, in-situ, multi-frequency soil content sensors is presented. The underground sensor, that contains a small metamaterial inspired antenna that doubles up as a sensing element, measures the impedance of the surrounding soil by sending multiple signals of known frequencies in the range 1-40 MHz and comparing the magnitude and phase of reflected signal to those of incident signal. The amplitude and phase values that represent the reflection coefficient are stored in an internal register. In each transmission cycle, this packet is transmitted to an over ground receiver. The receiver decodes the data and processes it to extract the impedance value at the sensing element. The impedance values are then used to extract soil contents by solving certain dielectric mixing and relaxation models. A user-friendly graphical interface is developed that can support the automation of the whole process, and display the estimates of soil content as the output to help an end-user make effective decision about irrigation and fertilization.