Evaluation of array calibration methods for DOA estimation in presence of ground, mutual coupling and near zone objects

Performance of several techniques for array calibration in order to estimate the direction of arrival (DOA) of the incoming signals in the presence of mutual coupling, ground reflections and near zone objects is evaluated. It is shown that the calibration method based on the signal subspace approach cannot estimate the DOA when the angle of the signals varies in a wide range of azimuth angles. Also it is shown that the ground reflections and near zone objects have remarkable effect on the calibration methods which are based on the actual radiation patterns of the array elements such as using the universal steering vector (USV). In fact, changing the distance of the array from the ground plane and scattering objects destructs the array calibration.