Research On Spectrum Estimation Algorithm Based On Orthogonal Dipole Pair Array

The Direction of Arrival(DOA)estimation of signals is an important part of passive direction finding(DF)technology.Subspace algorithms such as the Multiple Signal Classification(MUSIC)algorithm,are capable of distinguishing multiple signals within the same beam.The good DF performance is based on that the incident signal is not correlated or the correlation is low.However,there are a large number of coherent signals in the actual environment,which leads to the failure of the traditional feature space based spectrum estimation algorithm.Moreover,such algorithms have low direction finding accuracy under the influence of various factors such as small snapshot,low signal to noise ratio(SNR)and channel mismatch.Therefore,it is of great engineering significance to reduce the influence of some parameters in the algorithm on the system DF error and study the decoherence algorithm.In this paper,the problem of joint parameter estimation of signal DOA and polarization parameters based on orthogonal dipole pair array is deeply studied.Some solutions and improvement schemes are proposed for some problems existing in existing algorithms,including:1.Aiming at how to avoid the direction error caused by channel inconsistency,a rotating bi-orthogonal dipole pair array and its DOA and polarization information joint spectrum estimation algorithm are proposed.By rotating the array elements,the positions of the elements corresponding to each sampling point are different,and the polarization-sensitive uniform virtual array can be obtained;By sampling the output data of the rotating array element,the received data vector of the virtual array can be obtained;Finally,combined with the rankdeficient MUSIC algorithm,the joint estimation of the incident signal DOA and polarization information is completed.The polarization-sensitive rotating array proposed by the algorithm contains only two orthogonal dipole pairs,which has a high utilization of array elements.It can effectively reduce the size of receiving system and signal processing system,and to some extent avoid the influence of channel inconsistency on DF results.The array proposed in this paper is applicable not only to orthogonal dipoles,but also to other polarization-sensitive antenna elements,and has strong portability.Computer simulation experiments verify the effectiveness of the proposed array.2.Aiming at the constraints of classical decoherence algorithm,a joint parameter estimation algorithm for incident signals under sparse Bayesian framework is proposed.The main ideas of the algorithm are as follows: 1)Construct a signal-space-polarized domain sparse array model,and use the unitary transform to make it real-valued;2)Introduce the Gauss-ExpChi2 three-layer prior as the prior probability distribution of the model parameters,which promotes the sparse solution of the signal vector matrix;3)Based on the variational Bayesian theory,the mean and variance of sparse vectors satisfying the stopping condition of iteration are obtained by alternating iterations when the Kullback-Leibler(KL)distance is the smallest.4)The power spectrum function is constructed according to the mean and variance,and the DOA of the signal can be solved by the corresponding peak value at the maximum point;5)The polarization information of signals can be estimated by using the DOA and modulus constraints.