| The high frequency surface wave radar works in the frequency band of 3-30 MHz,and the over sight detection target is realized by using the diffraction effect of electromagnetic wave on the earth surface.The Multi-Input MultiOutput(MIMO)system is combined with the high frequency surface wave radar,and the multi-carrier frequency MIMO radar technology is adopted to effectively integrate multiple directions by taking advantage of the difference of target RCS of different frequencies and angles.The multi-carrier frequency echo information can overcome the target scintillation,and also improve the frequency utilization rate of high frequency surface wave radar in the limited frequency band.At the same time,using the advantages of MIMO system greatly reduces the occupation area of the antenna,so as to achieve the goal of miniaturization of high frequency surface wave radar system and the improvement of radar detection capability.Based on the practical system of the transceiver integrated high frequency surface wave radar,this paper has carried out relevant research on the virtual aperture expansion,beamforming and angle super-resolution of MIMO-HFSWR with multi-carrier frequency,and verified by the measured data.The details are as follows:Firstly,the principle of uniform linear array beamforming of traditional phased array radar is introduced,and based on this theory,the model of uniform linear array of multi-carrier frequency MIMO signal is established,and the basic principle of multi-carrier frequency MIMO signal is described.The mechanism of virtual array processing under multi frequency system of uniform linear array model is studied.The directional function of the uniform linear array of multi-carrier frequency MIMO signals is derived.The influence of different frequency combinations on beamforming performance of multi-carrier frequency MIMO signals is simulated and analyzed.Then,based on the existing beamforming of multi-carrier frequency signal,aiming at the gate lobe problem caused by the space under sampling due to the excessive frequency interval,the paper continues to study the cubic spline interpolation algorithm to homogenize the heterogeneous virtual array synthesized by the receiver of multi-carrier frequency MIMO high-frequency surface wave radar.The best square triangle approximation algorithm based on Fourier transform is proposed,which has better effect on beamforming when the signal-to-noise ratio is lower.Based on the angle super-resolution of single carrier frequency,the advantages and disadvantages of multi-carrier frequency signals in the angle super-resolution of array element domain are analyzed.The performance of angle super-resolution of MIMO nonuniform virtual array is studied by using cubic spline interpolation algorithm and the best square triangle approximation algorithm based on Fourier transform.On this basis,the music algorithm of beam domain angle super-resolution is proposed,which further improves the angle measurement accuracy of radar system.Finally,according to the actual test of the transceiver integrated miniature high frequency surface wave radar system,the beamforming of the multi-carrier frequency MIMO-HFSWR virtual array and the improvement of the performance of the angle super-resolution algorithm in the beam domain to the target detection resolution and angle measurement precision of the actual system are verified by the measured data. |
PDF Full Text Request