Multipath Mitigation Using Circular Rotating Antenna

As we all know that multipath is one of the main error sources that degrade the quality of the Global Navigation Satellite System (GNSS) receiver observables. On the other hand, the use of Geostationary Earth Orbit (GEO) satellites in some of the systems results in extremely low multipath fading frequency which brings new challenge to multipath mitigation. The multipath of the GEO satellite has extremely low fading frequency, which makes some of the post-receiver-measurementbased multipath mitigation techniques ineffective. These traditional techniques are designed based on the characteristics of the multipath of Medium Earth Orbit (MEO) satellites, whose fading frequency is much higher than that of the GEO satellites. Based on the two-path environment with one direct path and one indirect path, we analyzed the characteristics of the multipath error and fading frequency caused by antenna circular rotation. Based on the relationship between the phase lock loop correlator output amplitude variation and the code multipath error when the antenna rotates, we proposed an amplitudeweighted code tracking loop that can reduce the code multipath error with low fading frequency which is hard to be remove by traditional loop filter. The experiments using the data from GNSS signal generator and the real data collected from the rotating platform verify our proposed method.