Radio Frequency Interference Suppression And Its Effects On The Current Inversion In Distributed High Frequency Radar Network

Compared with the traditional Marine monitoring method,Spatial Distributed high frequency over the horizon radar network has the advantages of high precision,large area,strong continuity and real-time detection.This radar system provides the wide-area real-time sea state detection with technical support.However,the radar echoes are usually degraded due to radio frequency interference(RFI).RFI has the characteristics of range-domain correlation and doppler-domain spectral broadening,the interference may submerge the sea echo from different radar stations,lead to the error in ocean surface radial flow inversion result,and then affect the detection performance of radar system.Mathematical model is established based on single frequency RFI,the physical characteristics of RFI are analyzed statistically.The RFI suppression algorithms are discussed and their effects on the correction of radar echoes are analyzed.The effects of RFI impacted on with the inversion of radial current is discussed by simulation.The main contents of the full text are as follows:1)This paper introduced the structure and the waveform parameters of spatial distributed high frequency over the horizon radar network,setting predetermined range and frequency offset,the echo spectrum of each radar in network is arranged in one range-Doppler spectra window.The radial current inversion methods for monostation and bistatic radar mode are introduced.2)Using the measured data analyzed the common characteristics of radio frequency interference in the experiment.Radio frequency interference distribution characteristics in time-spatial domain and frequency-range domain are deduced based on a mathematical model of single frequency RFI.SVD algorithm is introduced to suppress RFI in time-spatial and frequency-range domains,respectively.It is applied to the experimental data of HF radar network.The results show that the suppression on interference amplitude in frequency dimension is better than that in range dimension,while the performance of SNR is better for suppression in range dimension.3)The effect of suppression algorithm on RFI is verified further by the comparison of current inversion with and without applying the algorithm.Simulations are conducted,simulation results show that RFI will induce wrong current or make the information of current be wrongly taken as noise leading to the loss of current in some region.Interpolation algorithm can improve the inversed current results significant but can't recover the lost current completely.Furthermore,frequency dimensional SVD algorithm works better in suppressing the effect of interference on radial current magnitude usually leads to loss of radial current information.While the spatial dimensional SVD algorithm have better performance in suppressing effect of interference in the directional information of inversed current.