Introduction

Ultra-Wideband (UWB) is an emerging wireless communication technology that was recently allowed unlicensed operation by the FCC in the 3.1-10.6 GHz frequency band [1]. FCC specifies a minimum signal bandwidth of 500 MHz or a fractional bandwidth of 0.2, whichever is less. The transmitted power is, however, constrained to be below the Part 15 limit (-41.25 dBm/MHz) for indoor unintentional radiation (see the FCC mask in Fig. 1(a)). For all practical purposes, this ensures that the UWB signals look like noise to the narrowband receivers already co-existing in the allocated band.

Figure 1: (a) FCC mask for EIRP emission (-) from UWB systems and the Part 15 limit (-.-). (b) Issues affecting the design of a Pulse-Radio UWB system.

[a] [b]

Pulse-radios are wireless devices that communicate through short-duration, wide-bandwidth discontinuous signals (pulses). This work focused on digital pulse synthesis techniques. Challenges specific to UWB pulse radio design (Fig. 1(b)) were studied and new architecture based solutions were proposed [2]. Fig. 2(a) gives an overview of the techniques presented in this work. A frequency plan was also devised which utilized one fixed clock frequency and generated different 500 MHz wide pulses in the 3.1-10.6 GHz FCC band.

Figure 2: (a) Broadband Sampling-image cancellation techniques proposed in this work. (b) UWB pulses each occupying 500 MHz wide channels within the FCC mask. Fast switching between different 500 MHz wide pulses covers the entire UWB band while avoiding significant group-delay distortion.

[a] [b]