| High frequency surface wave radar has become a major tool for continuous monitoring and tracking of maritime targets with the advantages of over-the-horizon detection,all-weather use and wide monitoring area.Shipborne high frequency surface wave radar has the characteristics of flexibility and freedom from site restrictions.It can carry out real-time monitoring of maritime targets in the more open sea area while the ship continues to navigate,so it has become an effective supplementary means to traditional detection methods in the application of ocean remote sensing detection.Limited by the size and tonnage of the shipborne platform,the number and size of the antennas of the shipborne ground wave radar are much smaller than the antenna array of the shore-based ground wave radar,which makes the azimuthal detection accuracy of the shipborne ground wave radar for ship targets poor.Synthetic aperture technology utilizes the relative movement between the radar and the target to equivalently synthesize a small-aperture antenna into a virtual large-aperture antenna,which can improve the resolution of the azimuth.In order to improve the azimuth resolution of shipborne ground wave radar,the synthetic aperture technique is applied to the direction-finding of shipborne high frequency surface wave radar and the theoretical study is verified by simulation experiments in this paper.The main contents of this paper are as follows:1.This paper gives the basic model of direction-finding of high frequency surface wave radar array antenna and analyzes the principle of array antenna direction-finding.The DBF algorithm and MUSIC algorithm for high frequency surface wave radar direction-finding are derived,and the direction-finding performance and accuracy of the two algorithms are analyzed and compared by simulation experiments.Finally,the direction-finding analysis is combined with the high frequency surface wave radar measured data,and the data from the ship's AIS is used to assist verification.2.The synthetic aperture technique is applied to shipborne high frequency surface wave radar direction-finding by using the characteristics of shipborne platform motion.This part analyzes the principle of synthetic aperture technology,establishes the model of shipborne high frequency surface wave radar synthetic array,derives the echo signal model of the target under single-array element and multi-array element synthetic aperture for shipborne platforms,and analyzes the effects of ship speed,platform movement distance and length of synthetic array on target azimuth resolution with DBF algorithm.Simulation results show that combining shipborne high frequency surface wave radar with synthetic aperture technology to synthesize small aperture antennas equivalently into large aperture antennas can effectively improve the azimuth resolution.3.An algorithm using virtual array synthesis technique is proposed for the detection of ship target azimuth in shipborne high frequency surfacewave radar echoes with sea clutter interference.For the problem of sea clutter echo spectrum spreading due to shipborne platform motion,the circular pair elimination method and orthogonal weighting algorithm are used to suppress it.After suppressing the sea clutter spreading,the proposed virtual array synthesis algorithm is used to complete the direction-finding.Simulation results show that the use of this algorithm can improve the azimuth resolution of shipborne high frequency surface wave radar in the sea clutter background. |
PDF Full Text Request