Calibration of directional mutual coupling for antenna arrays

Mutual coupling (MC) is one of the major error sources in array signal processing. The previous methods mostly assume that the MC is direction-independent and it is modeled by a single MC matrix. However, this is not valid in a practical scenario where the effect of MC differs for the source signals incoming from different directions. In this paper, calibration of directional MC is considered for direction-of-arrival (DOA) estimation problem. An alternating and sectorized parameter estimation (ASPE) algorithm is proposed where the estimates of the source DOA angles and the MC coefficients corresponding to each source direction are found iteratively. A unified approach is introduced so that the proposed algorithm can effectively work for different array geometries regardless of the array geometry and the corresponding MC matrix model. The performance of the proposed method is evaluated by several experiments and it is compared with the conventional calibration techniques as well as the Cramer-Rao lower Bound which is derived for the considered problem. It is shown that the proposed method effectively finds the unknown source and coupling parameters and it has superior performance as compared to the conventional calibration techniques.