antenna for its enabling high
data transmission rates, low power consumption
and simple hardware configuration in communication
applications such as radio frequency identification
devices, sensor networks, radar and location
tracking, etc[1]. The UWB antennas of such systems
are also required for small size, non-dispersive and
wideband properties. Its commercial applications of
the frequency band from 3.1 GHz to 10.6 GHz were
approved by the Federal Communications Commission
(FCC) in America in 2002. Beside the
consideration of ultra wideband performance, the
design of antennas for UWB communication also
need a band-rejection filter to avoid the interference
with existing wireless networks with standards
such as IEEE 802.11a in U.S.A. (5.15~5.35 GHz,
5.725~5.825 GHz) and HIPERLAN/2 in Europe
(5.15~5.35 GHz, 5.47~5.725 GHz)[2]. As a result,
UWB transmitters can not cause any electromagnetic
interference on nearby communication