Satellite coverage for GPS antennas on small spinning projectiles

In this paper, the satellite coverage of GPS antennas on a small, highly dynamic spinning projectile is investigated. Since the projectile has varying pitch and roll, the antenna needs to have omni-directional coverage. A patch antenna is selected as the basic element, but it by itself cannot provide the necessary coverage. To obtain the desired coverage, multiple elements are placed around the circumference of the projectile. Then, we investigate the best way to combine the responses of the elements to provide good SNR coverage. The three reception modes we study are digital beamforming, simply summing the elements together (we will call it sum mode), and choosing the element with highest SNR (we will call it diversity mode). Beamforming has the ideal performance but is costly because one needs to know the antenna manifold and satellite angle of arrival. The array mode does not need this information but leads to much lower SNR. The diversity mode also does not need this information, and recovers much of the ideal performance and has 4-10 dB minimum SNR improvement upon the sum mode. The diversity mode, therefore, may be a good choice for spinning projectiles.