UWB Antennas for Wireless Applications

Currently, there is an increased interest in ultra-wideband (UWB) technology for use in sev‐ eral present and future applications. UWB technology received a major boost especially in 2002 since the US Federal Communication Commission (FCC) permitted the authorization of using the unlicensed frequency band starting from 3.1 to 10.6 GHz for commercial com‐ munication applications [1]. Although existing third-generation (3G) communication tech‐ nology can provide us with many wide services such as fast internet access, video telephony, enhanced video/music download as well as digital voice services, UWB –as a new technology– is very promising for many reasons. The FCC allocated an absolute band‐ width up to 7.5 GHz which is about 110% fractional bandwidth of the center frequency. This large bandwidth spectrum is available for high data rate communi-cations as well as radar and safety applications to operate in. The UWB technology has another advantage from the power consumption point of view. Due to spreading the ener-gy of the UWB signals over a large frequency band, the maximum power available to the antenna –as part of UWB sys‐ tem– will be as small as in order of 0.5mW according to the FCC spectral mask. This power is considered to be a small value and it is actually very close to the noise floor compared to what is currently used in different radio communica-tion systems [2].