Research On The Non-cooperative Detection Technology Of Ultra Wide-band(UWB) Impulse Radio Signals

Ultra-Wide Band (UWB) signals in this dissertation is restricted in UWB impulse radio (UWB-IR) signals.UWB systems rely on ultra-short (nanosecond scale) impulse pulse waveforms of low duty ratio that can be free of sine-wave carriers and transform information via time-hopping(TH) or direct spread(DS) technology. Comparing to traditional radio systems, UWB systems own lower power density of frequence (PDF) and wider bandwith, which can provide extremely high data rate and good property of anti-jamming. For impulse pulse often be covert in environmental noise or the other jamming, UWB exhibits low probability of detection (LPD), which be used in military domain especially. UWB signals are adopted by the military communication of high data rate, low probability of interception (LPI) data link between an unmanned aerial vehicle(UAV) and a ground station, and high resolution radar/location systems.Under the condition of non-cooperative reception, the research on detection technology of UWB signal has important military signification.This dissertion is focused on the detection problems of UWB radio signal under the condtion of unknown or partly known apriori information, while signal-to-noise ratio (SNR) is below 0dB. The main work follows below:While the input SNR is below 0dB and apriori information are all blind, we study the detection methods of UWB signal based on Hilbert-Huang transform (HHT). The conclusion shows that HHT is superior to traditional wavelet transform and Wigner-Ville distribution.For the different property between signal and noise in the intrinsic mode function (IMF) domain, IMFs product detector is proposed. Under the condition of low SNR and the unknown distribution of noise, Simulation shows that IMFs product detector is superior to Teager energy operator (TEO) detector. Refering to Rosenfeld subband product theory, IMF domain filter (IMFDF) is developed and used in the edge detection. In contrary to wavelet transform domain filter, IMFDF is more simple, and has less complexity.The measurement rule of coss correlation of input (signal add noise) and output (CCIO) for blind signal detection is proposed. And then, two methods of UWB signal detection via parameter-induced aperiod stochastic resonance (PASR) are presented.While the input signal matches the output signal of PASR system, phenomena of stochastic resonance is more prominent. So, we proposed CCIO measurement methods, which is different to Collins cross correlation methods.Using linear response theory (LRT), the theoretically performance of CCIO is deduced. While the input SNR is below -10dB and the signal is all unknown, the detector based on PASR via CCIO measurement can work well.Under the rule of CCIO measurement, code sequence detection methods of DS-UWB signal via PASR system are developed. For lower SNR DS-UWB signals, the performance of PASR detector is inferior to matched filter (MF). On the contrary, if there is large error of desychronisation, performance of PASR detector is superior to MF.Under the rule of CCIO measurement, the PASR multiple windows detector (PASR-MWD) is proposed to detect the TH-UWB signals. The results show that the performance of the PASR-MWD is inferior to MF, while superior to multi-radiometer and IMFs product detector when the input SNR is below 0dB.If there is no apriori knowledge and the SNR is below 0dB, the methods of piecewise auto-correlation accumulation (PACA) for the detection of UWB signals is presented. After rigorously mathematical deduction, some valuable conclusions are drawn: at the multiple times of symbol period, discrete peaks of the PACA function appear with 3 peaks in group, which includes a larger peak located in the middle and the other smaller two located symmetricly beside the larger one. The distance between small peaks is modulation offset of pulse position PPM. The simulation shows that enhance the accumulation time, the detection of UWB signal under 0dB is feasible.If the symbol period is known only, the methods of detection UWB code sequence waveform based on the eigenvalues decomposition(EVD) is developed. The distribution of eigenvalue and eigenvectors of the covariance matrix of UWB signal is deduced theoretically. The estimation methods of TH-UWB code sequence based on EVD are proposed especially.The phenomena of appearing 3 eigenvectors corresponding to 3 bigger eigenvalues reflects the sum of 2-arry TH symbol's waveform in the asynchronous situation for TH-UWB systems. The error lemma of estimation of code sequence via matrix perturbation theory is proved. At last, the relations among the error of estimation, the input SNR, and the number of accumulation windows are analyzed.