Overcoming RFI with high mask angle antennas and multiple GNSS constellations

Radio frequency interference (RFI) has been being a significant issue for global navigation satellite system (GNSS) users. An increasing number of satellites in multiple constellations enable users to use high mask angle antennas (HMAAs) to reduce RFI from terrestrial sources. This paper studies the optimal antenna mask angle that maximizes the suppression of RFI but still maintains the performance of a single constellation with a low mask angle antenna. The paper first introduces a novel lower bound on expectation of DOP. Our theoretical analysis based on the lower bound generates a closed-form expression that directly relates DOP to the antenna mask angle and the average number of visible satellites. Then, we conduct numerical simulations based on actual and planned GNSS orbits. The optimal mask angles obtained from theoretical analysis highly agree with the simulation results based on similar assumptions. The theoretical and simulation results show that two constellations can match performance of one with 5-14° higher mask, and three constellations can match performance of one with 11-23° higher mask, depending on the DOP metric and the range error model used. The results also show diminishing marginal gain of mask angle obtained with the increase in number of satellites. In addition, using HMAAs is more beneficial to users interested in positioning accuracy than users interested in time transfer accuracy.