We propose a framework based on the use of a flat-base Luneburg lens antenna with a waveguide array for Direction-of-Arrival (DOA) estimation, and also present a hybrid approach which combines waveguide mode extraction and signal processing techniques for enhancing the angular resolution of the lens antenna. The hybrid method involves sampling the electric field at specified positions when the lens is operating in the receive mode, and extracting the weights of the possible propagating modes in each waveguide. Following this, we correlate these weights with the known ones that have been derived by either simulated or measured signals from single targets located at different look angles, to make an initial estimate of the angular regions of possible DOAs. We then apply an algorithm based on the Singular Value Decomposition (SVD) of the simulated or measured database to estimate the angles of incidence. Numerical results show that the proposed framework, used in conjunction with the hybrid approach, can achieve an enhanced resolution over the conventional limit base on the 3 dB beamwidth of the lens antenna. Furthermore, it is capable of locating targets with different scattering cross-sections and achieving an angular resolution as small as 2˚, for a Luneburg lens antenna with an aperture size of 6.35λ and a Signal-to-Noise Ratio (SNR) of 30 dB.
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