Research On Subcarrier-Domain Adaptive Filtering Approaches For High-Frequency Passive Bistatic Radar

The high-frequency passive bistatic radar(HFPBR)uses electromagnetic waves emitted by HF non-cooperative illuminators to detect and track the corresponding targets.Compared with the traditional HF active radar,it has the advantages of antiinterference,no frequency spectrum occupation,covert surveillance and low cost.With the development of digital broadcasting and as the only non-patent digital broadcasting in the high frequency band,digital radio mondiale(DRM)broadcasting,which uses orthogonal frequency division multiplexing(OFDM)as its modulation technology,on the one hand,is increasingly popular in the world,and on the other hand,has thumbtype ambiguity function,which provides a good foundation for the study of DRMbased HFPBR.In the signal processing of DRM-based HPPBR,the surveillance channel signal has the serious multipath clutter including direct-path wave,zeroDoppler-shift multipath clutter and non-zero-Doppler-shift multipath clutter.This will cause the desired target echo to be submerged,so these clutter needs to be suppressed to highlight the target echo.Based on the research of the existed clutter suppression algorithms,combined with the waveform features and clutter characteristics,novel adaptive clutter filtering approaches based on subcarrier-domain are proposed.The specific research contents are as follows:(1)Started with the usual receiving signal model of DRM-based HFPBR,this paper theoretically analyzes the principle,advantages and disadvantages of conventional time-domain adaptive filtering algorithms,block adaptive filtering algorithms and extensive cancellation algorithms.Furthermore,it paves the way for the following new adaptive clutter filtering approaches.(2)Aiming at solving the problem that the conventional time-domain adaptive filtering algorithms have large filter order value and high computational complexity when rejected zero-Doppler-shift multipath clutter,further combined with the multicarrier modulation features of OFDM waveform and utilized the correlation of zero-Doppler-shift-multipath clutter at the same subcarrier frequency in subcarrier-domain,subcarrier-domain adaptive zero-Doppler-shift multipath clutter filtering approaches based on iterative filter are proposed innovatively.From the complex products and actual effects of the approaches,it can conclude that the approaches can observably reduce the computational complexity and availably improve the clutter suppression performance.(3)Aiming at solving the problem that conventional clutter suppression approaches can't consider the non-zero-Doppler-shift multipath clutter,combined with the multicarrier modulation features of OFDM waveform,utilized the correlation of multipath clutter with the same Doppler shift at the same subcarrier frequency in subcarrier-domain and utilized the difference between the Doppler shift of the target and the non-zero-Doppler-shift multipath clutter in some specific situations,subcarrierdomain adaptive non-zero-Doppler-shift multipath clutter filtering approaches based on iterative filter are proposed.The simulation and experiment results prove that the approaches can reject the zero and non-zero-Doppler-shift multipath clutter.