Research On Ionospheric Clutter In-terference Characteristic In HFSWR

Compared with traditional radar, HFSWR has some advantages, such asover-the-horizon detection, all-weather and large-scale application, and low cost.Therefore, it has gained a growing application in military and civil fields. However, dueto the relative concentration of high-frequency communication, broadcast, and atmos-pheric noise in short-wave frequencies, various channels, and limited spectrum re-sources, HFSWR tends to be affected by external interference or even can’t workproperly. In addition, ionosphere interference can hardly be eliminated as it comes in allshapes, propagates in different paths and doesn’t change obviously. Some unknownsignals and wave clutters also affect the process. Therefore, it has become an importanttopic among experts from home and abroad that how to suppress interference effectivelyand enhance the detection performance. At present, many countries have studied HF ra-dar ionosphere interference resistance extensively. However, there is no effective way todeal with all kinds of problems by now. To address the problem, this paper will analyzeand research it from the following aspects:First of all, formulate the operating principle of HF radar, classification of radarinterference, solving methods of radar array pattern, and theory of radar polarization.Furthermore, this paper makes a comparative study of the time-frequency analysismethods, including principles, merits and demerits, applicable occasions of differenttime-frequency analysis, such as STFT, wavelet transform, and Wigner-Ville distribu-tion.Secondly, give the optimal algorithm by analyzing the interference in HF radar andthe actual situation of HF radar’s data processing. Based on the above analysis, we canactually process HF radar data as follows. First, process the data by using orthogonali-zation, filtering, channel consistency compensation, matched filtering of P4code, dis-tance and speed disposing, and getting the distance-speed spectrum. Second, process thedata by using time-frequency analysis, getting characteristics of targets and interfer-ences. Third, calculate all direction angles of points in the distance-speed spectrumwhich has a certain power, get direction characteristics of targets and interferences, andanalyze its statistical features. Fourth, calculate all polarizing angles of points in thedistance-speed spectrum which has a certain power, get polarizing characteristics oftargets and interferences, and analyze its statistical features.Finally, process HF radar data by using methods of time-frequency analysis，arraypattern，and polarizing angle, and analyze radar pulse signal and different characteristicsof targets and interferences in the distance-speed spectrum to lay a foundation of elimi-nating the interference in future. The result of MATLAB simulation validates the cor-rectness and applicability of the algorithm.