Research On Target Detection Based On Passive Bistatic Radar

Passive Bistatic Radar(PBR)only consists of the receiver and does not transmit any signal for detection,but relies on the radiation source located at separated place to detect the target.The PBR has the advantages of good concealment,high resolution and low system cost and played an increasingly important role in electronic reconnaissance and has become an important field of research.There are the following problems of PBR: The direct wave was not controlled by the receiver.The side peaks can be found in Digital Video Broadcasting-Terrestrial(DVB-T)signal.The power of the direct wave and multipath were much greater than that of the echo.The main content of this thesis includes:At first,the advantages and the workflow of the PBR were discussed,the signals can be used as external radiation source and several performance parameters of PBR have been discussed.Then,the feasibility of DVB-T signal as the external radiation source signal was analyzed.The DVB-T signal is modulated by orthogonal frequency division multiplexing(OFDM).The advantages and disadvantages of the DVB-T signal used as the radiation source of the PBR were discussed.The computer simulation for DVB-T signal without the pilot and the Transmission Parameter Signaling(TPS)has been made.After that,taking the DVB-T signal as an example,the pretreatments of external radiation source signal and echo of PBR for detection were carried out.The purification of direct wave,preprocessing of reference channel and interference cancellation were analyzed theoretically and verified by simulations.During the process of direct wave purification,the traditional adaptive filter was replaced by Constant Modulus Algorithm(CMA),then the straightforward wave can be purified without any prior information.Then we improve the CMA by using the step parameter with the error information to resolve contradiction between the convergence speed and error.In the process of reference channel,since the ambiguity function of the DVB-T signal is not ideal,the position of the side peak can be found by analyzing the TPS information,then remove the intra-symbol side peaks by an equalizer and the inter-symbol side peaks by the filter,then the side peaks can be eliminated.In the process of interference cancellation,Extensive Cancellation Algorithm(ECA)was produced.The echo will be projected into the subspace consisted by the direct wave extracted from reference channel and its delay replica.Batch vision of Extensive Cancellation Algorithm(ECA-B)was produced to reduce the computational complexity of ECA.Then try to eliminate the harmonics that may occur in the Doppler shift domain by improving the ECA-B.The performance of these algorithms have been compared through simulation work.At last,The position of the target can be obtained by analyzing the time difference of arrival of the echo signal with respect to the reference signal;the velocity of the target can be obtained by analyzing the Doppler shift of the echo signal with respect to the reference signal.