Extended long-short ambiguity resolution in multi-antenna GNSS-over-fiber systems for enhanced attitude determination

An extended long-short ambiguity resolution (AR) approach to multi-antenna GNSS-over-fiber systems is proposed and experimentally demonstrated, providing enhanced attitude determination. GNSS signals are remotely acquired from M extended antennas and then transferred to a central node. Through virtual baseline processing, multiple baselines with intermediate length are constructed. Consequently, although the adjacent baseline ratio is limited, the overall aperture is expanded. The carrier phase measurements of equal length virtual baselines are averaged by following the parity detection process for reducing noise, leading to refined baseline estimation. Also, the extended long-short AR method is a single-epoch and search-free one, enabling both improved accuracy and real-time implementations. Both the AR success rate and accuracy of baseline estimation are remarkably enhanced, thus resulting in enhanced attitude determination. Full 3-D attitude determination is also possible with the proposed angle-type or cross-type planar array. In the experiments, the ambiguity is successfully resolved for more than 1400 epochs. The standard deviation of the baseline vector is reduced to almost one-third in both horizontal and vertical directions, without specific delay monitoring hardware.