Design of low-profile omnidirectional antenna for ground sensor networks

A new technique for designing an omnidirectional antenna that resembles a monopole antenna is presented and discussed. The antenna features less then lambda/7 in diameter and less then lambda/100 in vertical height. This approach allows placement of this antenna in a wide variety of environments while maintaining low-profile and preserving its input impedance and radiation behavior. Due to such capacity, the antenna is capable of being used for ground sensor networks. The fabricated antenna displays excellent matching and low cross-polarization radiation levels. Despite its relatively low radiation gain and efficiency, it is shown additional improvements can be made by increasing the height of the cavity and using materials with low dielectric constants.