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Multistage direction‐of‐arrival estimation approach for noncoherent and multigroup coherent signals

A new multistage direction estimation (MSDE) method using two parallel uniform linear arrays (ULAs) is proposed, which estimates two‐dimensional (2D) direction‐of‐arrivals (DOAs) of a mixture of noncoherent and multigroup of coherent signals, sequentially. At first, we estimate 2‐D DOAs of noncoherent signals, next, utilize an iterative procedure to make the estimation accuracy better, then omit the effect of noncoherent signals by the oblique projectors. Now, to estimate the 2D DOAs of each group separately, the group with the minimum coherent signals is decorrelated by the forward spatial smoothing, then an initial 2D DOA estimation is calculated and the estimation accuracy of this group is improved by using an iterative procedure. Afterward, the information of the signals whose DOAs are estimated, is omitted by oblique projectors. We repeat in the same way until the 2D DOAs of all coherent groups are estimated. It is shown in the simulation results section that the proposed method has good performance.