Spectral shape of UWB signals - influence of modulation format, multiple access scheme and pulse shape

This paper studies how to design the spectrum of a UWB signal in accordance with the FCC regulations and IEEE 802.15.3a recommendations. We show that the "conventional" UWB system with pulse-position modulation and time-hopping multiple access gives rise to spectral lines that violate the regulations. The impact of different modulation and multiple access schemes on the spectrum shaping is derived from the power spectral density of a non-linear and memoryless modulation. Detailed theoretical and simulation results stress the difficulties raised by the use of dithered pulse trains. We thus propose several solutions to achieve compliance with the FCC spectral masks.