Research On The Method Of Passive Detection And Location Of Small UAVs

In recent years,with the popularity of UAV,the safety problem caused by UAV becomes more and more urgent.Radio monitoring of UAV is an effective method for UAV control.The direct sequence spread spectrum(DSSS)communication is widely used in UAV communication due to its high channel capacity and strong anti-interference ability.The detection and parameter estimation of the DSSS signal is a key research topic.The UAV control has a high timeliness requirement.How to locate the position of the UAV quickly and accurately is also an important problem to be solved.Firstly,the basic principle of the direct-sequence communication system is introduced.The mathematical model of the direct-spread signal is analyzed.And the pseudo-random sequence used in the direct-spread signal is studied.Secondly,several widely used methods for DS signal detection and parameter estimation are discussed.In terms of carrier frequency estimation,frequency doubler method is analyzed.For symbol period estimation of pseudo-random codes,the autocorrelation method,the spectrum reprocessing method and the cepstrum method are studied.In terms of symbol rate estimation,delay and multiply approach,cyclic spectrum and wavelet transform methods are discussed.Thirdly,the passive location of UAV is studied.The working principle of various positioning methods is briefly discussed.And the multi-station TDOA positioning is chosen as the positioning method.Chan solution method and Taylor series method of TDOA location are deduced.Finally,the influence of various factors on the TDOA positioning accuracy in the UAV positioning scenario is analyzed,and the improvement method is presented.In the end,the measured signal is collected and analyzed.The acquisition process of the measured signal is discriped.The method described in Chapter 3 is tested on the measured data,and the information such as the repetition period,carrier frequency,symbol rate,and symbol width of the measured signal is estimated.The detection methods is used on the noise signal and the other kinds of signal in the measured data to show the effectiveness of the detection method.The performance differences of different methods on measured data are compared,and the difference of performance of the same method on measured data and simulation data is compared.To solve the problem of BPSK signal demodulation,a demodulation method based on wavelet transform is proposed,and the effectiveness of this method is demonstrated by simulation.