Beamforming Algorithm For Wideband Digital Reconnaissance Receiver

The digital reconnaissance receiver is facing adverse electromagnetic environment in the modern electronic warfare.Analyzing and processing the captured signal has become an important topic in the field of electronic reconnaissance.At the same time in order to cope with larger bandwidth and more types of digital signal,digital reconnaissance receiver used digital beamforming technology to obtain the instantaneous spatial coverage and high resolution good.This paper study the beamforming algorithms of wide-band digital reconnaissance receiver.The main research work are described as follows:1.The model of narrowband and wideband signal is analyzed,and the receiving model of array signal and the basic knowledge of beamforming are expounded.Three classical narrowband beamforming algorithms are simulated and analyzed.2.The wideband beamforming algorithms based on frequency domain are researched,including ISM,CSM.The optimal focusing matrix and focusing frequency are given for the CSM algorithm.Finally,aiming at the large bandwidth characteristics of the digital reconnaissance receiver,and the main lobe width,the maximum sidelobe level and the beam direction of the antenna pattern under different algorithms and different bandwidth are compared.3.The design method of fractional delay filter is introduced.The wide-band beamforming algorithm based on fractional delay is studied.The advantage of fractional delay filtering based on Farrow structure is analyzed.Because the fractional delay filter based on the Farrow structure does not need to update the filter coefficient with the beam direction change,it is more suitable for the beamforming in electronic reconnaissance.We simulated broadband beamforming based on fractional delay filter,integer delay filter and the conventional phase shift form.And vertify the fractional delay compared to integer delay beam forming superiority.4.The gate suppression technology based on virtual array is studied.We combines virtual array technology and broadband beamforming algorithm to solve the problem of grating lobes on broadband DBF.Digital reconnaissance receiver can cover several frequency bandwidth,If the array element spacing in accordance with the highest frequency signal of half wavelength as array element spacing,there will be serious inter element coupling.And if the array element spacing in accordance with the lowest frequency signal of half wavelength,the high frequency signal grating lobes appear serious.EAVA and TAVA two kinds of virtual array technology are researched to solve the above problems.Two technology does not need to know the prior knowledge of the reconnaissance signal,it use two kinds of algorithm that has fast calculation of virtual array signal,then the algorithms through the LS(least square)algorithm get reasonable covariance matrix to beamform.Finally,the simulation of S band(2-4GHz)radar signal is carried out.The results show that the two algorithms can suppress the signal gate lobe and reduce the width of the main lobe,improving the angular resolution of the digital reconnaissance receiver under the same number of real array element.