Mode-ESPRIT for DOA estimation using a dual-mode antenna array

The problem of direction-of-arrival (DOA) estimation using an array of multiple identically oriented dual-mode antennas is addressed. A new mode-estimation of signal parameters via rotational invariance techniques (ESPRIT) algorithm is presented, it uses rotational invariances between two subarrays of different modes in which the rotational factors depend only on the DOA of signal. This method requires no information about the element positions and removes the constraint of the traditional spatial-ESPRIT on the array spatial geometry. A multi-scale mode-ESPRIT variant for sparse arrays is further given for the case of known element positions, to produce high quality but unambiguous DOA solutions by fusing two sets of DOA estimates. Numerical results are given to illustrate the performance of the proposed algorithms.