Ultra-wideband (UWB) communication systems have become an attractive wireless topic since the Federal Communication Commission (FCC) first approved in 2002 the rules for the 3.1 -10.6 GHz unlicensed band for commercial UWB communications utilization . The high demands on such a communications system have stimulated research into many UWB antenna designs. Nonetheless, antenna designs for UWB applications face many challenges including their impedance matching, radiation stability, compact size, low manufacturing cost and electromagnetic interference (EMI) problems. The EMI problems are quite serious for UWB systems since there are several other existing narrowband services which occupy frequency bands within the designated UWB bandwidth. These include world interoperability for microwave access (WiMAX) service from 3.3 to 3.6 GHz; wireless local area network (WLAN) services such as IEEE 802.11a in the USA (5.15 to 5.35 GHz, 5.725 to 5.825 GHz) and HIPERLAN/2 in Europe (5.15 to 5.35 GHz, 5.47 to 5.725 GHz); and satellite services near 8 GHz. To avoid the interference with these coexisting systems, a UWB antenna which has intrinsic filtering properties at such service frequencies is necessary to mitigate the potential interferences. It is highly desirable for them to be intrinsically handled rather than through an external band-stop filter device to minimize the footprint of the antenna system, the signal processing requirements, and the cost.