Design of Archimedean Spiral Antenna for Wireless Underground Sensor Network

In this paper, the antenna suitable for a wire-less underground sensor network is designed in Ansys High Frequency Structure Simulator (HFSS). The dielectric properties viz. dielectric constant and loss tangent of four different types of soil with different clay contents and different volumetric water contents are found from the Mineralogy Based Soil Dielectric Model (MBSDM). These dielectric properties are then used to simulate the different types of soil by creating a mud box to emulate the underground soil scenario. One antenna is kept 6cm above the ground and another antenna is kept 28cm below the ground inside the mud box. The simulation is performed for four different soil types to determine the attenuation between the two antennas caused by the different types of soil using HFSS. The gain of the antennas above and below the ground is observed and tabulated for different types of soil. An Archimedean Spiral Antenna is designed and simulated to determine the attenuation between the antenna 6cm above the ground and the antenna 28cm below the ground. The attenuation is found to be within 15dB - 30dB for all four types of soil. This range of attenuation is acceptable for a precision agriculture wireless underground sensor network application. The return loss and gain of the antenna are found to vary when used in different soil types based on the clay content and volumetric water content of the soil.