Rapid ultra-wideband signal acquisition

Low transmission power and a highly spread bandwidth makes the acquisition of ultra-wideband (UWB) signals a difficult problem. In a packet-based network employing UWB modulation in the physical layer, long preambles need to be prepended to each packet because the low signal power requires the receiver to process the signal for long periods of time in order to estimate the timing of the signal. The long spreading or hopping sequences used in UWB systems result in a large search space for the acqusition system at the receiver. This paper presents a signal acquisition system for UWB which employs a hybrid signaling format involving direct sequence (DS) spreading and time hopping (TH), significantly reducing the search space in the UWB acquisition system. The acquisition system employs equal gain combining (EGC) which enables the utilization of the energy of the dense multipath, typical of a UWB channel. The performance of the acquisition system has been analytically evaluated and is corroborated through simulation.