Coherent DiLL for direction of arrival estimation

Recently, a new direction of arrival (DOA) estimation scheme, direction lock loop (DiLL) was proposed (see Hou, W. and Kwon, H.M., Proc. IEEE Vehicular Technology Conference, 2000; Min, S. et al., Proc. CDMA Int. Conf., 2001). It is configured to operate in noncoherent mode, in other words, it uses an amplitude squaring of the spatial correlator output. As a result, there is squaring loss due to amplitude squaring in noncoherent DiLL (N-DiLL). A new DOA estimation scheme, coherent DiLL (C-DiLL), is proposed. C-DiLL utilizes the real part of the spatial correlator output, and its performance is better than that of N-DiLL. The use of the real part in C-DiLL makes it possible that two branches of spatial correlators in N-DiLL are merged to one branch. However, C-DiLL needs to estimate carrier phase and transmitted data. The DOA estimation accuracy and tracking capability of C-DiLL are investigated by computer simulations, in comparison with those of noncoherent DiLL.