Recognition And Suppression Of Ionospheric Interference In High Frequency Surface Wave Radar

As High Frequency Surface Wave Radar(HFSWR) is not only able to monitor a wide range of wind field, ocean currents and wave field on sea surface in all weather, but also able to detect sea-surface target and low-altitude flight, it is of great value to effectively monitor the exclusive economic zone. Due to operation frequency band of High frequency surface wave radar in a complex electromagnetic wave environment, various kinds of interferences such as radio interference, ionospheric interference, etal exist in this band will seriously degrade detection performance of HFSWR. Ionospheric interference is a main interference and it is difficult to suppress as it is complex, time-varying and similar to target.Ionospheric interference formation mechanism of HFSWR and its propagation mode and typical ionospheric interference form is described based on layered structure of ionosphere. Impact of ionosphere to HFSWR frequency selection is analyzed. Ionospheric interference character in time-domain, frequency domain and range domain are mainly analyzed and provide a theoretical support for ionospheric interference recognition and suppression.This paper proposed a region clustering based ionospheric interference recognition method in time-domain and provincial characteristics based ionospheric interference recognition method in R-D spectrum based on analysis of time domain feature, range domain feature and frequency domain feature of ionospheric interference. The two methods are able to recognize ionospheric interference in time domain and in R-D spectrum and provide effective ionospheric interference location for suppression of them so as to get a more accurate suppression result and make it available in real application.Ionospheric interference has a characteristic of directivity and different directivity has an important effect on selection of suppression method so this paper proposed an ionospheric interference suppression method with combination of multiple method based on directivity of ionospheric interference. The proposed method select certain method to suppress ionospheric interference based on intensity of directivity, and combined different methods to suppress complex ionospheric interference with both strong directivity and weak directivity. Experiment result shows that the proposed method is able to effectively suppress ionospheric interference.