Research On Error Calibration Method For Conformal Array

A conformal array antenna is an array which conforms to the object shape. Compared to conventional planar array, conformal array not only meets the performance requirements of itself, but also takes into account the aerodynamic characteristics of the carrier. Because of the advantages of the conformal array, the conformal array can be widely used in radar, communication, navigation and other related fields. The array error will greatly affect the performance of spatial spectrum estimation. And a lot of calibration algorithms are proposed to solve this problem for planar array. However, due to the non-uniform element pattern, these classic error calibration methods can not be applied to the conformal array. Therefore, it is significant to research the error calibration methods for the conformal array. In this dissertation, two array error calibration algorithms are proposed to accurately estimate the source angles for the conformal array in the presence of array perturbations. The main contents are as follows:Firstly, the signal model of the planar array is established, and the basic characteristics of uniform linear array and uniform circular array are described in detail. Then, the signal model of conformal array and the array error model are also established. The influence of array errors is analyzed by the experiment. Typical active array errors calibration and self-calibration method are also introduced here. The simulations verify the effectiveness of the two methods.Secondly, an effective error calibration method is proposed for circular conformal array in the presence of array errors including the mutual coupling error, gain-phase error and position error. These errors can be equivalent to the angularly dependent gain-phase error. In the algorithm, the whole array and the corresponding airspace are divided into several sub-arrays and sub-airspaces to avoid the shadow effect of the conformal array. Several assistant sources are set in different directions respectively. The angularly dependent gain-phase error can be estimated by the method that requires calibrating sources in each sub-airspace. So we can reconstruct the actual array manifold of sub-arrays for the corresponding sub-airspaces based on the angularly dependent gain-phase errors estimation. Through the reconstructed array manifold, the angle of the sources can be well estimated. Simulation results demonstrate the superior performance of the proposed algorithm.Finally, a self-calibration method based on the cylindrical conformal array in the presence of the mutual coupling error is proposed. By using reducing dimensions thought, the 2-D direction of arrival (DOA) estimation can be accomplished by individual 1-D DOA estimation of the elevation and the azimuth, which utilize the estimation of signal parameters via rotation invariant technique (ESPRIT) and the Rank-reduction (RARE) methods, respectively. Moreover, the mutual coupling coefficients can be well estimated after getting the DOA estimates. Simulation results verify the effectiveness of the proposed algorithm.