Research On Direction Finding Techonlogy Of HF Radio In Complex Environment

In recent years,Radar Direction of Arrival Estimation Approach has been a hot topic.With the in-depth study of various methods,this technology has gradually become mature.At present,working frequency band of HF radar is very limited,the relatively tight working frequency band has become more crowded due to the rapid growth of frequency demand.The use of various types of radio signals makes the electromagnetic environment worse and worse,and the interference phenomenon is also becoming more and more serious.The shortwave radio which works in this frequency band has a great influence on the normal operation of radar receiver.If l Direction of Arrival of the jamming radio can be estimated and the jamming azimuth can be obtained,the jamming frequency band of the radar signal can be avoided when selecting the working frequency band of the radar signal,and it can be used normally in other areas.Thus,the frequency selection of the signal is guided.n this paper,the azimuth estimation of jamming radio is realized by using spatial spectrum estimation technique.At the same time,the complex situations such as impulse interference and fewer snapshots in the signal are considered,and the compressed sensing technology is used to realize the direction estimation of single snapshots,the elimination of impulse interference and signal recovery of LFM signal.Firstly,the DOA estimation of signals is modeled and analyzed,The classical spatial spectrum estimation algorithm MUSIC(multi-signal classification)is simulated,and the advantages and limitations of MUSIC algorithm in DOA estimation are analyzed.,and theoretical research is done to accurately realize DOA estimation of measured signals.Then,in view of the possible shortage of snapshots,compressed sensing technology is used to model and analyze the signal direction estimation model in single snapshots,and the gradient descent coefficient recovery algorithm is used to estimate the signal direction of arrival,and the advantages and disadvantages of the algorithm are simulated and analyzed.The accuracy and resolution of coherent signal and incoherent signal under different algorithms are analyzed and compared.Aiming at the problem that MUSIC(multiple signal classification)algorithm has low accuracy in estimating coherent signal,the spatial smoothing MUSIC algorithm is introduced to realize azimuth estimation of coherent signal.Next,the impulse interference signal in the measured signal is analyzed and considered.For a specific LFM signal,considering that the LFM signal is sparse in the optimal fractional Fourier transform(FrFT)domain,the transform order is determined.Using the compressed sensing theory,the original signal can be recovered from part of the signal,and the combination can be set.The reasonable measurement matrix can suppress the interference when only part of the data is observed.The signal can be reconstructed by eliminating strong interference and using sparse reconstruction.Finally,the measured data are processed in full frequency band,and the azimuth of jamming signal at different frequency points is obtained,so as to realize the guidance of frequency selection for radar signal.