Research On Array Calibration Method For Monostatic And Bistatic Multi-frequency HF Ground Wave Radar

HF(High-Frequency)ground wave radars are required to continuously improve the measured accuracy and increase the area coverage with the development of technology for the remote sensing of the ocean surface.It has become a developing trend for monostatic and bistatic Multi-frequency HF ground wave radar to jointly monitor the coverage sea area.However,because of the use of antenna array for direction finding,HF ground wave radar system is vulnerable to antenna manufacturing technology,antenna array surrounding environment,receiver channel mismatch and other factors.Based on monostatic and bistatic Multi-frequency HF ground wave radar system,this paper concentrates on the array signal model formulation by the formation mechanism of array errors,while several methods,such as nonlinear fitting,iteration optimization,information theory criteria and other algorithms,have been used to realize the array active or passive calibration.The effectiveness of the proposed algorithm is confirmed by the measurement data sets to thus improve the reliability of radar echoes.First of all,we introduce the geometric characteristics and operational principle of monostatic and bistatic radar,in which the signal processing technology of linear frequency-modulated interrupt continuous wave is expounded,and the Bragg frequency shift relation between the monostatic radar and bistatic radar is given.Based on the analysis for the formation mechanism of array signal and errors,the ideal and actual array signal models are formulated.The ocean scattering mechanism of HF electromagnetic waves is described,and the first-order sea echo of monostatic HF ground wave radar is analyzed by numerical simulation.Through the descriptions and analyses of several typical estimation algorithms of DOA(Direction of Arrival)and their characteristics,a regularized iterative optimization algorithm is proposed about the DOA estimation.The proposed algorithm is assessed its accuracy and stability with numerical simulation for these DOA estimation algorithms.The above discussions lay a solid theoretical foundation for the array calibration in the HF ground wave radar.Then,for the calibration of bearing-dependent array errors,the array calibration methods are studied and analyzed for Multi-frequency HF ground wave radar system,and the relation between the applied array calibration method and its array geometric structure,as well as the advantages and disadvantages of various calibration methods are pointed out.By these analyses,the array signal model of the phased array is established,and an array calibration method with nonlinear fitting and array manifold interpolation is proposed based on AIS(Automatic Identification System)information.In the measured data sets processing,the AIS information and radar echoes are matched to obtain the ship echoes with known bearings,MUSIC(MUltiple-SIgnal Classification)algorithm is used to estimate DOAs of the ship echoes with and without calibration,and the results verify the effectiveness of the proposed calibration algorithm.For the calibration of bearing-independent array errors,the array calibration methods are studied and analyzed for Multi-frequency HF ground wave radar system,and the identification of parameter estimation,algorithm complexity,global convergence,the difference and relation of various calibration algorithms and the reference source types for calibration methods are discussed.On these bases,the array signal model of the phased array with channel amplitude-phase errors is established,and a passive calibration method based on the first-order sea echo is proposed by the eigenstructure method,damping Newton method and Lagrange multipliers method.In order to ensure the reliability of array calibration,the quantity of samples with a single-angle situation is statistically analyzed in array calibration initialization.By studying extraction methods of the first-order sea echo with a single-angle situation,the information theory criterion method is introduced to extract targets with a single-angle situation.In the numerical simulation and experimental data processing,based on the ship echoes with known bearings,MUSIC algorithm is used to estimate the DOAs of the ship echoes with and without calibration,and the results show that the proposed calibration method is effective and real-time.Next,we introduce the basic geometric relation of a bistatic HF ground wave radar system,and study the detection method of range,velocity and bearing under the bistatic mode.On these bases,the Doppler spectra of the first-order sea echo for the bistatic HF ground wave radar are analyzed by simulated and measured data sets,the analysis results show that the simulated spectra and measured spectra have a good agreement.Then,the bistatic measured data sets are analyzed by the passive calibration method.The preliminary analysis results show that the proposed array calibration algorithm can be used in shore-based bistatic HF ground wave radar system.Finally,conclusions are included in the end.The array signal model formulated and the proposed array calibration methods can solve the problems existing in the actual array system,which have a certain application value.It also points out the future research in the end.