Design of Omnidirectional UWB Antennas for Communications
As was shown in Chapter 3, many UWB antennas have been designed to have ominidirectional radiation patterns. However, like other antenna parameters, conserving this feature with low variations over the operational ultra wideband bandwidth is a difficult task. In Chapter 2 we explained that the directionality (which is related to the gain) of an antenna is determined by its radiation pattern, provided it describes the spatial distribution of energy radiated or received. Thus, it is desirable that the gain is constant or quasi-constant for a wide range of frequencies.