A weighted combining method for GPS antenna diversity

GPS signal detection and parameter estimation are compromised in attenuated and harsh multipath environments. Diversity schemes are viewed as a method to alleviate the multipath fading phenomenon and to enhance signal detection and parameter estimation performance by providing additional processing gain. In this paper, the performance of a weighted diversity combining method for the spatial antenna diversity system is analyzed and compared with the equal gain combining method. The combining methods are performed at two different levels namely the correlator output and the measurement level. The performance of the proposed method is empirically tested with live GPS L1 signal in a harsh indoor environment. Detection performance is assessed through a comparison of Receiver Operating Characteristic (ROC) curves. The parameter estimation accuracies are compared by analyzing the differential pseudorange standard deviation. Accuracy of the local level position solution is also evaluated to investigate the performance at the navigation level. It is shown that the accuracy of positioning by the proposed weighted combining method utilizing the spatial diversity is significantly improved compared to the individual diversity branches.