Two-dimensional direction-of-arrival estimation method based on interpolation fitting for airborne conformal MIMO radar in a multipath environment

Abstract

This paper shows a novel two-dimensional direction-of-arrival (2D DOA) estimation method which is based on the interpolation fitting (IF-based) algorithm for airborne conformal MIMO radar with unknown polarization in a multipath environment. Since the backscattered propagation paths from the same target include the direct path (DP) and indirect paths, we can separate the DP signal and indirect path signals from the range bins in signal detection. Therefore, target signals at different range bins can be adopted to measure the 2D DOA, respectively. Each conformal sensor is composed of one electric dipole distributed on the geometric surface of the airborne platform, which requires the 2D DOA estimation is carried out in the case of unknown polarization. Aiming at the problem of 2D DOA estimation with unknown polarization, the IF-MUSIC method is used to measure the 2D DOA through the 2D angle search vector preprocessed by a designed interpolation fitting matrix which can project the 2D angle and 2D polarization state subspace of conformal polarization sensitive array into the 2D angle subspace. To further improve the estimation accuracy, the fusion technology based on the variance minimization criterion is employed, which can obtain the optimal weight coefficients of different path signals. The proposed method needs one channel in each sensor and there is no mutual coupling effect inside the sensor. Finally, numerical experiments verify the high-precision 2D DOA estimation performance.