| High Frequency(HF)passive bistatic radar is a new type of radar system which exploits existing transmitters as illuminators of opportunity to perform target detection and track.HF passive bistatic radar combines the multiple superiorities of HF radar with passive radar,which can effectively improve the performance of target detection,reduce the running cost,realize over-the-horizon range propagation simultaneously,and supply a powerful support for our nation's new detection radar system.With the rapid development of digital signal and the digital signals taking place of the traditional ones.In the future,DRM broadcast signals may become the mainstream digital broadcasting signal in our country.This provides a convenient condition for the researches on passive radar based on DRM broadcast signals.This paper investigates some problem of clutter rejection for HFPBR based on the DRM.The propagation mechanism and signal model of this radar system are analyzed.After analyzed the problem of the target detection,especially analyzed the most important issue--clutter rejection.And then,basing on the summarizing and analyzing the commonly useful algorithms,the clutter rejection ability and convergence of the conventional time domain algorithm are quantitatively compared;and the feasibility of the conventional air domain adaptive algorithm are qualitatively analyzed.Using the point that the DRM signal exploits the multi-carrier modulation technique,the spatial,temporal and carrier-domain array signal model of passive bistatic radar is established;corresponding clutter suppression algorithms based on the orthogonal-frequency-division-multiplexing(OFDM)signal structure is studied;based on sub carrier time domain orthogonal subspace projection theory(ECA-C)is analyzed in-depth,an extended ECA-C suppression algorithm is proposed.Using the subspace orthogonal projection for suppression of both the multipath clutter with zero and non-zero doppler frequency shift.Then this paper analyzes the advantages and disadvantages of spatial domain and time domain algorithm,a combined adaptive spatial and time domain algorithm is proposed,this algorithm overcomes the shortcomings of insufficient array degree of freedom and the ECA-C algorithm lack of target azimuth gain,which can effectively improve the detection ability of weak targets.The proposed space-time domain combination adaptive technology is used to process the simulated and measured data by taking DRM digital AM broadcast based passive bistatic radar for example.And it is proved that the proposed technology is practical,which provides a theoretical and experimental basis for the clutter rejection of OFDM external radiation source radar in other frequency bands. |
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