Research On Target Information Extraction For Digital Broadcast Based Passive Radar With A Single Channel

Passive radar,a kind of bistatic/multistatic radar system,exploits the third-party transmitters as illuminators of opportunity to perform target detection and tracking.It has many notable advantages,such as being friendly to environment,covert operation,spectrum saving,easy networking,cost-controllable and so on.The coherent processing technology is adopted in the passive radar system,which sets surveillance channel and reference channel to receive the target echo signal and the reference signal,respectively.Differing from the typical passive radar,the single-channel passive radar(SPR)only has a single receiving channel,which is used as the reference and surveillance channel simultaneously.Therefore,while retaining the advantages and characteristics of the passive radar,the SPR is more compact for its using fewer hardware devices,which is more conducive to system miniaturization and deployment,and has great value to study and has good prospects for application.Based on advantages such as radiated power,wide bandwidth and good low altitude coverage,digital broadcasting signal has gradually become one of the effective illuminators of opportunity for the passive radar.This paper focuses on the extraction of target information in the single-channel digital broadcasting based Passive Radar(SDPR),where two detection modes are studied.For the non-forward scattering detection,the detection performance of the SDPR is evaluated and the multistatic SDPR networking detection scheme is proposed.The target information extraction methods using frame header and frame body of digital broadcast signal are researched.For the forward scattering detection,the extracting method of target doppler feature is studied,and then the echo spectrum characteristics of the multi-rotor UAV is analyzed.The main contributions of the dissertation are as follows:1)The detection performance of the SDPR is evaluated,and a multistatic SDPR(MSDPR)processing scheme is proposed.Firstly,the influence of the reference purity on signal processing performance is analyzed in detail.The relationship between the SDPR detection performance and the purity of the extracted reference signal as well as the energy of direct-path signal is deduced.Combining with the pattern of the receiving antenna,the detection performance of the SDPR is evaluated.And the detection power of the SDPR under different experimental scenarios is given.Considering that the SDPR cannot locate and track the detected target,a novel MSDPR detection scheme based on shared reference signal and the specific implementation method are proposed.The scheme can obtain the optimal reference signal,improving the detection capability and reducing the cost.The scheme is validated by MSDPR experiments.2)The target information extraction based on digital broadcast signal frame body is researched.To extract the reference signal in the complex propagation environment,a reference signal reconstruction method based on constellation focusing under low SNR is proposed.To suppress the non-zeros Doppler multipath clutter,combined with the characteristics of OFDM modulation of digital broadcast signals,the frequency-domain extensive cancellation algorithm by carrier(ECA-C)method is emphatically discussed.To accurately estimate the time-of-arrival(TOA)of the direct-path signal,a joint processing method based on the empirical threshold value method and the calibration method is given.The MSDPR experiments are carried out and the experimental results under different multipath environments are given to verified the proposed methods.3)The target information extraction method based on Pseudo-random Noise(PN)signal is studied.An idea that exploits the known PN signal in the digital television terrestrial multimedia broadcasting(DTMB)system as a new illuminator of opportunity for the passive radar is proposed.Firstly,the detection performance of the PNPR(PNbased passive radar)is analyzed,which shows the locally remapped PN reference signal could make the mismatched ambiguity function(AF)present an ideal thumbtack shape.Then,combined with the characteristics of PN signal,a processing method without the multipath clutter cancellation is proposed.The processing method uses the received PN signal and the locally remapped PN reference signal to perform the circular crosscorrelation operation,and uses the statistical mean method to suppress the additional interference introduced.This processing method has low computational complexity and is suitable for parallel processing.Finally,the theoretical considerations and proposed algorithm are validated via both the simulated and experimental data.4)Based on the conventional hardware architecture of non-forward scattering detection,a method of Doppler feature extraction in forward-scatter area is studied.The method uses the received baseband complex signal to extract the coherent “reference signal” through the hard decision.And then signal mixing,frequency interception and direct-current removing are used to attain the target echo signal,which simplifies the hardware architecture,decreases computational load and has strong robustness.Then the echo spectrum characteristics of the multi-rotor UAV in the forward scattering region are analyzed.A method of wavelet decomposition is used to separate the highfrequency components of the echo spectrum,which are beneficial to the target classification.The field experiments on different scenarios are carried out,and the detection results of different types of targets using different frequency bands of digital signal sources are analyzed,which verifies the effectiveness of the proposed method.