  Rapid advancement of antenna technology catalyses the popularization of
extremely large-scale multiple-input multiple-output (XL-MIMO) antenna arrays,
which pose unique challenges for localization with the inescapable near-field
effect. In this paper, we propose an efficient near-field localization
algorithm by leveraging a sectored uniform circular array (sUCA). In
particular, we first customize a backprojection algorithm in the polar
coordinate for sUCA-enabled near-field localization, which facilitates the
target detection procedure. We then analyze the resolutions in both angular and
distance domains via deriving the interval of zero-crossing points, and further
unravel the minimum required number of antennas to eliminate grating lobes. The
proposed localization method is finally implemented using fast Fourier
transform (FFT) to reduce computational complexity. Simulation results verify
the resolution analysis and demonstrate that the proposed method remarkably
outperforms conventional localization algorithms in terms of localization
accuracy. Moreover, the low-complexity FFT implementation achieves an average
runtime that is hundreds of times faster when large numbers of antenna elements
are employed.
