Ultra-wideband Communications System Hidden And Non-cooperative Detection Techniques,

IR-UWB systems rely on ultra-short(nanosecond scale) impulse pulse with low duty ratio that can be free of sine-wave carriers.Comparing to traditional narrowband systems, UWB systems own lower power spectrum density(PSD) and wider band,which can provide extremely high data rate and the feature of strong anti-jamming.For UWB signals often be hidden in the noise,UWB exhibits low probability of detection(LPD),which make it a promising candidate for future tactical military radio networks.Under the condition of non-cooperative reception,the research on detection technology of UWB signal has important military signification.The thesis adopts the pseudo-random and chaotic sequence as TH code and DS code for UWB system,and derives the PSD of a modulated TH-UWB and DS-UWB signal. Based on qualitative assertions,by the analysis of the PSD,we achieve assertions how multiple accesses impact covertness of UWB.The covertness of UWB signals has been analyzed through theoretical analysis and simulation comparison.Since there are not the unified standards to measure the covertness, through the comparison of a variety of measurement methods,the study mainly used radiometer to analyse the covertness,and a multi-radiometer for IR-UWB signals also be adopted.The criterion of evaluation of the covertness used in this dissertation is detectability distance.The covertness of UWB signals,the narrow signals,DS-SS has been carried out,the main system parameters selection methods has been proposed to enhanced the IR-UWB system's covertness.Without any priori knowledge,it's difficult to detect signals by use of a multi-radiometer.A method of the fluctuations of second-order correlation statistics estimators for the detection of UWB signals is presented.Though strictly mathematical derivation and simulations,it has been known that discrete peaks of the fluctuations of second-order correlation statistics estimators own periodical variation which can be used to evaluate symbol period and modulation offset of PPM.