Research On DOA Estimation In Wireless Location System Of Smart Antenna

In wireless location system based on mobile communication base station, the longitude and latitude coordinates of mobile end are acquired by analyzing the antenna array signals, and marked its on the electronic map. Unlike the wireless location technology system based on GPS, the mobile terminal in wireless location system based on mobile communication base station does not require with GPS function, location of the mobile terminal is determined only by measuring the distance between the mobile terminal and base station.In this thesis, the commonly algorithms of estimating the distance between the mobile terminal and the base station are analyzed, including:(1) Time of Arrival(TOA);(2) Direction of Arrival(DOA), or Angle of Arrival(AOA);(3) Time Difference of Arrival(TDOA); With the rapid development and wide application of smart antenna technology matures, DOA estimation method based on antenna array is adopted as a research direction to improve the positioning accuracy.After introducting the basic theory of antennas, antenna array and channel characteristics, traditional research method of DOA estimates are summarized. Basic principles of these methods are summarized, including Bartlett algorithm, Capon algorithm, MUSIC algorithm, ESPRIT algorithm. Mathematical model of each estimation method is established. Effects of noise impaction of these methods are compared by simulation. Experiments are carried out for 6 array element antenna with the array element spacing d=λ/2. Experiment results are given under angle of incidence by Matlab.Taking into account a large amount of calculation problems in MUSIC algorithm, accurate model is needed while solving the antenna array covariance matrix eigenvalues and eigenvectors, and the process of constructing orthogonal signal subspace and noise subspace. After analyzing the principles of traditional MUSIC algorithm and improved Root-MUSIC algorithm, to remove the affection of noise characteristics and reduce the amount of computation, root operation is applied to the minimum norm algorithm method, and formed the improved rooted minimum norm algorithm. Simulation experiments for six array element antenna array show rooted minimum norm algorithm can accurately analyze the arrival angle of 4 °, 8 ° incident signal at the same noise conditions, while reducing the amount of computation, to improve the positioning accuracy laid foundation.