PSD of UWB Signals

This document studies the Power Spectral Density (PSD) of time-hopping impulse radio (THIR) signals. The ”conventional” TH-IR system with pulse-position modulation and time-hopping multiple access gives rise to spectral lines that either violate the regulations, or require a significant power back-off. To remedy this situation, we propose the use of polarity randomization, which eliminates the spectral lines and also leads to a smoothing of the continuous part of the spectrum. We analyze the effect of symbol-based or pulse-based polarity randomization sequences on memoryloss modulation formats such as PPM, OOK and PAM. We provide a general demonstration of the spectral smoothing characteristics of these techniques without restriction on the definition of the TH sequences, and we discuss how finite sequences impact these results. This work may not be copied or reproduced in whole or in part for any commercial purpose. Permission to copy in whole or in part without payment of fee is granted for nonprofit educational and research purposes provided that all such whole or partial copies include the following: a notice that such copying is by permission of Mitsubishi Electric Research Laboratories, Inc.; an acknowledgment of the authors and individual contributions to the work; and all applicable portions of the copyright notice. Copying, reproduction, or republishing for any other purpose shall require a license with payment of fee to Mitsubishi Electric Research Laboratories, Inc. All rights reserved. Copyright c ©Mitsubishi Electric Research Laboratories, Inc., 2006 201 Broadway, Cambridge, Massachusetts 02139