The Research On Anti-jamming Algorithm Of Beidou Navigation Receiver

The BeiDou satellite navigation system(BeiDou Navigation Satellite System,BDS),which has been developed by China since 2000,as for the continually research and perfecting during the recent years,nowadays this system has been able to provide all-weather services such as high precision navigation,positioning and timing ect.in the entire Asia Pacific region.However,because of the inherent characteristic of the BeiDou navigation signal,while by the power restriction of the signals emitting by the BeiDou satellites,and the propagative distance of the receiving signals is very far,the arriving satellite navigation signals into the ground are very weak,such the weak signals can easily been affected by both accidental and intentional jamming signals at the BeiDou navigation receivers,eventually leading to satellite navigation and positioning is not accurate and even cannot locate.Therefore,in order to make the BeiDou navigation receivers working normally in the terrible electromagnetism jamming signal environment,we must first do the suppressing or decreasing jamming signals operation toward the receiving BeiDou signals.This thesis mainly studied the CSMG beamforming algorithm based on subspace projection,and an improved variable step size LMS space-time anti-jamming algorithm,through the two algorithms for suppressing the intense jamming signals toward the BeiDou navigation signals.The algorithm of the CSMG beamforming based on subspace projection,which is a combination of the Subspace projection and beam forming technology.Firstly,the data vector received by antenna array is projected onto the interference subspace,which is orthogonal to interference subspace for achieving interference suppression.And then,by using the method of the strictly constrained minimum power sampling matrix gradient(CSMG),after the projection of the subspace,the signal is beamformed in a fixed direction.Finally,for jammer-free data of each beam achieved to capture,locate,solute and so on.The ability of the suppress interference by this method,which can be more effectively,and keep the desired signal better.The improved variable step size LMS space-time anti-jamming algorithm,which is using an improved frequency filter to filter the narrowband interference from the desired signal direction in advance,meanwhile,an improved variable step Least Mean Square(LMS)method was proposed to complete the space-time array weights with fast iteration,thereby reducing computational complexity,and its complexity is significantly reduced.