Research On Anti-interference Technology Of Navigation Signal Based On Multi Domain

The power of satellite signal is very small when it reached user receiver,usually about-160 d BW,because satellites are very far away.At the same time,if the receiver receives a lot of strong interference signals,the performance of the receiver system will be poor,so it is very important to study algorithms to restrain interfering signals.This thesis mainly studies the Direction of Arrival(DOA)and the anti-interference algorithm of interfering signals,and the research results are as follows:In this thesis,a DOA estimation algorithm based on double parallel circular array antenna is proposed.Compared with a single-layer array structure,the double-layer circular array can construct the wave-direction matrix which includes the wave-signal space base.The pitch angle and the azimuth angle can be calculated directly by respectively using eigenvalues and eigenvectors which are obtained by decomposing the wave-direction matrix.This algorithm improves the resolution of the algorithm.On the issue of dealing with coherent sources,referring to spatial smoothing of Multiple Signal Classification(MUSIC)Algorithm,the covariance matrix can be restored to full rank by the virtual translation of the model along the axis of the center line.Computer simulation experiment proves that the method has higher resolution than unitary Estimation of Signal Parameters via Rotational Invariance Techniques(ESPRIT)method when multiple incoming directions are similar,signal-to-noise ratio is low,and small number of snapshots.In order to solve the performance degradation problem of the Power Inversion(PI)algorithm in dealing with coherent interference,we can estimate the interference angle by DOA estimation algorithm,and then add discrete random signal in the interference direction to improve the performance of the algorithm.In this thesis,a single-satellite constrained space-time anti-interference algorithm based on subspace projection is proposed.First,this method uses space-time domain structure instead of the space structure to solve the problem of the modified PI algorithm freedom which is limited by the number of elements.It can increase the degree of algorithm freedom by increasing the order of the domain filter behind each array.Second,the modified PI algorithm has no frequency domain resolution,and it may suppress the signal at all frequency points in the interference direction when processing the interference.To solve this problem,we can convert the signal from time domain to frequency domain,and then calculate the optimal weighted vector.Finally we can use subspace orthogonal projection technology to optimize weight.After these operations,the algorithm can suppress the interference signal at its corresponded frequency.Third,this article adds the constraint of useful signals to improve the problem which the modified Power Inversion algorithm may impair the useful signal when suppressing interference.Single-star constrained space-time anti-interference algorithm based on subspace orthogonal projection technique has better anti-interference performance than modified PI algorithm which was verified by computer simulation.