The Two-Loop Tracking Strategy for Real-Time Multi-Antenna GNSS Receivers

摘要

A multi-antenna global navigation satellite system receiver accepts many radio-frequency inputs simultaneously. Then, many antennas can be deployed on a vehicle and the receiver can decide which one is useful for the reception of each satellite's signal. As a consequence, navigation solutions can be obtained in more adverse conditions, but at the cost of an important increase of the receiver complexity. Particularly, tracking of the satellite signals is a challenging task in these receivers, especially when a variation in the vehicle's attitude impose a change in the antenna used for a satellite signal reception. Carrier tracking is critical during these changes of antenna since the distance between them is larger than the signal wavelength. Thus, a direct antenna commutation can produce important tracking transients that degrade the navigation measurements, affect data demodulation, and can produce a loss of signal tracking. The strategy presented in this work allows the receiver to keep tracking during these antenna commutations avoiding the detrimental tracking transients. Since it is based on close-loop schemes, it is suitable for real-time receivers due to their low computational complexity. The proposed technique is tested in a simulated low-earth orbit satellite scenario assuming a constant change of attitude due to a roll movement along the orbit direction vector. It is shown that a four-antenna receiver using the proposed tracking strategy can properly track the satellites in view, in spite of the frequent antenna commutations imposed by the vehicle's rotation.