Multi-antenna GNSS receiver tracking algorithm for vehicles with unconstrained three-dimensional motion

An algorithm for GNSS GPS/GLONASS receivers is presented that allows the receiver to seamlessly combine the inputs from multiple antennas during signal tracking in order to keep full sky visibility at all times. This algorithm has applications for both aeronautical and space applications in all kinds of vehicles with unconstrained three-dimensional motion capabilities: high maneuverability jet aircraft, rockets, satellites, unmanned aerial vehicles (UAVs), etc. The algorithm presented here keeps track of the received signal-to-noise ratios (SNR) and carrier phase on each of the antennas. For each set of correlation values the receiver selects the input antenna with the best SNR in order to do navigation message decoding and ranging. This fast-switching antenna selection process allows the receiver to stay synchronized with the incoming satellite signal for as long as at least one of the antennas of the set is within line-of-sight of the transmitting satellite. Distributing enough antennas throughout the fuselage of a vehicle, this algorithm will ensure that the receiver does not lose synchronization with the GNSS signals even during three-dimensional maneuvers like spins and attitude changes. This algorithm was implemented on a four-antenna GNSS receiver prototype hardware, and tested using a GNSS signal simula-tor. During these tests the multi-antenna tracking algorithm performed successfully. The results of some of these tests are presented in this paper.