Ultra-wide band low-profile spiral antennas using an EBG ground plane

Different from the traditional antennas for narrow-band systems, an Ultra Wide Band antenna provides new challenges for designers such as how to achieve the very wide impedance bandwidth (7.5 GHz) while still maintaining high radiation efficiency and minimizing the pulse distortion. Two Archimedean monofilar micro-strip antennas using Electromagnetic Band Gap (EBG) structure for UWB are developed in this paper. In these antennas, the EBG plays a role of ground plane of antenna in order to get a low-profile as well as unidirectional radiation. EBG also helps to improve the antenna performance significantly. In the first prototype, the uniplanar EBG structure is employed as a ground plane and in the second one, the mushroom EBG structure is embedded in order to enhance the antenna radiation pattern. The performance of two antennas is compared to the antenna using a perfect ground as well as is compared each other based on the simulation and measurement results.