I. Introduction
Ultra Wide Band(UWB) technologies are widely used in various applications such as ground penetrating radar systems, automotive collision avoidance system, wall-imaging systems, electronic jamming, wireless LAN, wearable computing and health monitoring, etc. UWB technologies will play more important role in the future due to their excellent advantages of wide RF channel, high data-rate, low transmission power, immune to multipath propagation, etc [1] - [3].