Research On Key Techniques Of Ultra Wideband Wireless Communication And Localization

Ultra-Wideband (UWB) Radio technology is one of the most rapidly developing, cutting edge research topics, and has attracted wide attention in the recent years. UWB radio occupies an extreme wide band in frequency domain and is considered as a potential candidate technology for the next generation of high data rate wireless communication over short distance. The technology is highly sought after in high-precision positioning systems due to its excellent time-domain characteristics such as high time resolution and strong immunity against multi-path fadding.This dissertation investigates the key techniques of M-ary spectrum spreading UWB communication and short-range high-accuracy positioning scheme using UWB signal. The main research contents and innovations can be summarized as follows:1. Two M-ary spectrum spreading UWB communication schemes using cyclic shifting pseudo-noise (PN) code and multiple-valued PN code are proposed. Since their communication signals is not generated by a single PN code, its spectrum has no discrete spectrum component, and appears to be smoother than the conventional spectrum spreading signals. Therefore, its signal can hardly be detected or intercepted by the conventional communication recon methods, and has better anti-jamming and anti-interception performance. Moreover, their signal can coexist with incumbent systems quiet well without causing significant interference. We have also researched fast synchronization capturing and high accuracy tracking technique in various application environments.2. After analyzing the advantages and difficulties of high precision ranging and positioning via UWB signals, three ranging and positioning schemes to overcome these difficulties which suit to different application environments are proposed, i.e., coherent timing via wire link, time difference among reference stations, time of round trip estimation using frequency-converted signal. Meanwhile, the channel model, link budget and the main factor influence to the positioning precision are discussed.3. A high precision symbol timing synchronization method based on variable group delay filter is proposed. The synchronization tracking loop based on variable group delay filter is combined with coarse synchronization acquisition using low-rate sampled signals, the time estimation precision can reach several percentage of the sampling interval. The method can be used to realize high precision symbol timing synchronization, which can conquer the bottleneck of difficult hardware realization with traditional methods, and lay a foundation for the implementation of the special UWB positioning chips. The computational complexity of the method is at least one order of magnitude lower than the conventional UWB TOA estimation.4. Through discussion of adaptive interference suppression technique for UWB devices, a parallel structure adaptive notch filter is proposed, which can effectively track and eliminate multi-band interference, and can extremely raise the jamming margin of a UWB M-ary spectrum spreading system when it is used as a preprocessing unit before dispreading. Besides, the filter structure has such advantages as simple structure, good stability, high convergence speed, low signal distortion and good suitability for FPGA implementation. Simulation results have validated the expected performance and properties.The dissertation also reviews the development and state of arts about UWB technology, and discusses the future prospects as well as some related issues worth to research.