Connectivity Improvement in Wireless Sensor Networks Using ESPAR Antennas with Dielectric Overlays

This article presents an electrically steerable parasitic array radiator (ESPAR) switched beam antenna with a dielectric overlay to miniaturize the antenna and modify the radiation pattern in the vertical plane. The antenna is intended for a gateway in a wireless sensor network (WSN) and is located on the ceiling of a room. Because the ESPAR antenna consists of an array of vertical monopoles, there is a deep minimum in the radiation pattern right beneath the antenna. The use of a dielectric overlay improves the radiation pattern in the vertical direction. Systematic tests in realistic indoor environment in the 2.4 GHz frequency band were conducted, which showed improved connectivity with wireless sensors placed near the floor in a wide area beneath the antenna.