| In recent years,high-frequency surface wave radar has made great progress both in military and civilian use.In the military field,high-frequency surface wave radar can prealert the trajectory of long-range sea surface targets and low-altitude aircraft targets due to its over-the-horizon detection,all-weather work and wide coverage.In civil use,highfrequency surface wave radar can realize real-time monitoring of the sea state environment and ocean current changes,which provides great convenience for people's production and life.The ionospheric clutter jamming technology has always been the research difficulty of high-frequency surface wave radar.The ionospheric clutter has the characteristics of non-stationary,wide coverage and high time variability,which has seriously affected the performance of high-frequency surface wave radar for sea detection,so ionospheric clutter suppression has become a popular research direction in the field of high-frequency surface wave radar.This subject has a different approach.From the perspective of target detection,the high-frequency surface wave radar system is used to detect the echo information reflected by the ionosphere,and then the position information of the ionospheric echo is estimated and studied.This provides reference for future generations to study ionospheric clutter suppression algorithm based on high-frequency surface wave radar system.This subject estimates and studies the ionospheric echo azimuth under the working system of high-frequency surface wave radar from two angles of theoretical derivation and engineering verification.First,this subject analyzes several practical ionospheric models based on the layered structure characteristics of the ionosphere,and studies the propagation characteristics of radio waves in the ionosphere,which provides a solid theoretical basis for subsequent research.Then from the theoretical research point of view,based on the international reference ionosphere model,this subject uses ray tracing technology to simulate and analyze the propagation trajectory of high-frequency radio waves in the atmosphere and ionospheric space.This subject also combines the maximum scattering theory and the ionospheric detection equation to estimate the azimuth information of the ionospheric echo.Next,from the perspective of practical engineering,this subject studies the azimuth information of the ionospheric echo under the working system of high-frequency surface wave radar.This subject uses a quasi-L receiving array composed of magnetic antennas to receive the echo information from the ionosphere.In this topic,the working principle and receiving pattern of the magnetic antenna are simulated and analyzed,and the feasibility of the magnetic antenna detecting ionospheric echo is verified.The amplitude and phase error of the actual receiving antenna array are corrected to realize the receiving channel,which ensures the consistent compensation of the receiving channel and improve the accuracy of radar angle measurement.Finally,based on the quasi-L-shaped receiving array,this subject uses the beamforming method to obtain ionospheric echo information with different horizontal azimuths and elevation angles.After the research and discussion in this paper,the ionospheric echo mainly comes from a large area in the zenith direction of the high-frequency surface wave radar launch system,while the signal of the ionospheric echo from the oblique and low-altitude sea directions returns to the high-frequency radar receiving system is relatively weak,and has little effect on the radar detection performance. |
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