DOA Estimation And Signal Synthesis For Distributed Subarrays Antennas

Distributed arrays antennas system is a new type sensor array system consisting of a plurality of spatially dispersed subarrays.It has many advantages such as strong maneuverability,flexible array scheme,and high direction finding resolution.Therefore,it has broad application prospects in the fields of radar detection,satellite positioning,and wireless communication.In this thesis,the high-precision Direction of Arrival(DOA)estimation of distributed arrays and the in-phase synthesis of signals in communication between distributed array and satellite are deeply studied.And several solutions are proposed for some key problems.The following is specific contents.Aiming at ambiguity resolution of distributed sub-arrays,this thesis proposes a DOA estimation scheme based on the dual-scale idea combining sum-difference beam algorithm and beam MUSIC algorithm.According to the algorithm,we firstly obtain a low-precision but fuzzy-free rough estimation by applying sum-difference beam algorithm to a single sub-array on small scales.Then,based on the rough angle estimation,the sub-array array elements are subjected to static beamforming processing to reducing the date scale of subsequent algorithm;Finally,using the processed data,we obtain a noise subspace constructing a spatial spectral function with an array manifold,search for a spectral peak of the spatial spectral function within the range determined by the rough estimation result,and finally obtain accurate direction estimation.The algorithm uses the fuzzy-free rough estimation result to limit the search range of the refined estimation,so that the illusory angle is not generated in the search range,which can solve the ambiguity.Compared with the dual-scale estimation of signal parameters via rotational invariance technique(ESPRIT),the proposed algorithm is not limited by the array manifold,therefore it is more applicable.The simulation results show that the proposed algorithm still has a threshold effect.Within the threshold range,the accuracy of direction finding increases with the distance between the sub-arrays of the distance.In this paper,the upper limit of the distance between sub-arrays is derived from the three dimensions of the pattern formula,signal source distance between signal source and signal bandwidth.In this thesis,signals synthesis of distributed subarrays antennas is discussed in two scales including in-phase signals synthesis of antenna array elements inside a subarray and the signals synchronous synthesis among subarrays.Inside a subarray,the classical beamforming methods can be used to compensate signals phase of array elements to achieve in-phase synthesis.Among subarrays,we can firstly calculate the relative delay of each subarray signal according to the direction of signal arrival and implement the preliminary delay compensation by sampling point interception,and then use the correlation of each signal for phase synchronization.SUMPLE algorithm is the most commonly used correlation algorithm for subarray antennas,but it suffers a shortcoming of phase drift.To solve this problem,this thesis proposes a improved SUMPLE algorithm about fixed reference sub-array signal phase,and its performance is verified by simulation.