Weak GPS signal acquisition using antenna diversity

Abstract

Signal acquisition is the first operation stage of a GPS receiver that detects the presence of GPS signals and provides a coarse estimate of the code delay and Doppler frequency. GPS signal acquisition becomes a challenging problem when the signal is subject to attenuation and multipath fading. In practice, standard methods such as extending the integration time without any aiding information to increase processing gain are not always sufficient to acquire weak signals. This difficulty can be characterized by the probability of detection, false alarm and mean acquisition time. This paper exploits spatial antenna diversity to mitigate the multipath fading effect in the acquisition process. Equal gain combining of two independent antennas is considered in a standalone processing strategy. The performance is evaluated in terms of Receiver Operating Characteristic (ROC). The theoretical analysis is compared with Monte Carlo simulations and real GPS data results. Experimental results demonstrate the improvement of detection probability and enhanced immunity against false alarms in dense multipath environments.