Low-Multipath Antenna for Real-Time High-Accuracy GPS in Earth and Atmospheric Sciences

Novel applications of high-accuracy GPS, such as GPS seismology and meteorology, require time-dependent, real-time, and near-real-time positioning at data acquisition times of only a few seconds. This fast observation rate enables the analysis of dynamic phenomena that are often encountered in Earth and atmospheric sciences. The most critical source of error in high-accuracy GPS, especially for dynamic applications, is multipath, the interference of multiple reflections with the direct GPS signal. For observations made over 24 hours, multipath effects can sometimes be removed by averaging, but for time dependent measurements performed over a few seconds there is currently no effective way to mitigate the errors introduced by multipath. Therefore, there is an urgent need for the development of new methods to reduce or eliminate this critical source of error for advanced GPS applications. The best way to mitigate multipath is to build an antenna that rejects multipath at reception. The only GPS antenna available today that can somewhat reduce multipath is the Choke Ring antenna. This antenna only partly rejects multipath (mainly at one frequency), presents a lower gain at low elevation angles, and is massive, heavy, and relatively expensive. In this work we propose and test a novel GPS antenna for real-time high accuracy applications. The antenna performance is enhanced through an innovative design of the antenna ground plane. GPS test measurements show that the proposed GPS antenna achieves an improved multipath rejection and eliminates multipath uniformly at L-Band, while allowing for a smaller and lighter antenna.