Stair-monopole antenna and irregular pentagon antenna in ultra-wideband applications: Detailed study

Ultra-wideband antennas are used in many communications, medical and military applications. Several ultra-wideband antennas were studied before as radiating elements taking into consideration the return loss only without studying the group delay or the radiation efficiency. In these mentioned publications, the antennas were classified as ultra-wideband according to their satisfactory return loss over the required bandwidth. However neither the group delay nor the radiation efficiency was investigated. The group delay and the radiation efficiency are key elements to measure the antenna performance, as large group delay will lead to pulse dispersion which will put a limitation on the data rate, while low radiation efficiency indicates high losses in the antenna structure. In this paper two previously published antennas are re-investigated. The antennas are fabricated on FR4 substrate and there is a good agreement between the measured and simulated return loss. The antennas return loss indicates no significant reflections in the FCC defined band regarding the ultra-wideband Transmission Systems. The radiation efficiency curves are used to identify the power radiated by the antennas. Finally the delay profile has clarified the ability of the antennas to be used in high data rate communications with very short duration pulses.