Chapter 5: Ultra-Wideband and Its Capabilities

5.1 Introduction

Ultra-wideband is a relatively new technology. The term UWB was introduced by the US Defense Advanced Research Project Agency (DARPA) only in the late 1980s [1]. Until recently, its development has been targeted at radar-and location-based applications. This is because the short pulse nature of the signal transmission results in very high-resolution timing information. However, ultra-wideband can also transmit large amounts of data (10s-100s Mbit/s) over a very wide frequency spectrum of a few GHz with a restricted power level <10 nW/MHz over short distance of a few metres. On 14 February 2002, the Federal Communications Commission (FCC) [2] lifted the restriction on the use of UWB technology for nonmilitary applications. New devices that incorporate the technology are now beginning to emerge as wireless LANs. With refinement of the technology, UWB systems will eventually be able to transmit data over a very high speed ranging from 400 Mbit/s to 500 Mbit/s [3]. UWB circuits need very little power to achieve these data rates (within the region of tens of mW), which is between one tenth and one hundredth of the power required by devices such as mobile telephones and existing wireless LANs for the equivalent data rate. This is ideal for battery-powered devices.

Unlike traditional narrowband systems, UWB generates short pulses and uses these pulses for data modulation. Therefore, UWB is alternatively referred to as impulse, carrierless or baseband transmission. However, it has now been realised that UWB does not have to be impulse...