Comparative Study of Spread Spectrum and Time Modulated Ultra-Wide-Band Communications

摘要

Ultra-wideband communications have recently received much attention. A number of military and commercial applications of ultra-wideband have been suggested. An ultra-wideband transmitter generates signals of very large bandwidths (in excess of gigahertzs) by transmitting nanosecond or subnanosecond pulses at baseband in some randomized fashion. As a result, an ultra-wideband system is in reality a baseband spread spectrum (SS) system with a very large spreading gain. Many of the characteristics and advantages of conventional SS communications carry over to ultra-wideband. For instance, a typical ultra- wideband system is capable of supporting multiple users, is robust against jamming and interference, is robust against multipath fading, and is suitable for applications requiring low probabilities of interception and detection (LPI/ LPD). On the other hand, the use of a very large bandwidth also imposes some new challenges, like wideband antenna design, acquisition design, and interference with other systems. The goal of this project was to provide an independent evaluation of the usefulness and effectiveness of Time-Modulated Ultra-Wideband (TM-UWB) for short- to medium-range communication in a battlefield environment. TM-UWB and SS were compared in three hypothetical application scenarios that are of interest to the Air Force: a cooperative attack weaponry system, an aerial surveillance system, and a buried facility probing system. Results showed a strong potential advantage of using TM-UWB in the buried facility probing system, for which a short-range, high-rate, low-power, wall-penetrating communication system is needed. For the other two scenarios of medium- and long- range communications, the advantage of using TM-UWB was not clear and needs to be further investigated. Ultra wideband appears to be best suited for systems with fairly short link ranges and it far outperforms its counterpart indoors. (16 tables, 37 figures, 23 refs.).