Design and analysis for an innovative scheme of SINS/GPS ultra-tight integration

Purpose – The purpose of this paper is to improve the tracking performance of the carrier phase lock loop (PLL) in the strapdown inertial navigation system/global positioning system (SINS/GPS) integrated system with an innovative scheme of ultratight integration. Design/methodology/approach – First, providing the Doppler frequency for PLL using SINS velocity could enlarge the loop equivalent bandwidth and reduce the dynamic effect on the carrier loop. Meanwhile, lowering the filter bandwidth could increase the immunity to noise. Second, the relationships between the PLL and SINS errors have been analyzed, and then the PLL error model is established to eliminate the correlation between the pseudorangerate error and SINS velocity error. Third, the carrier frequency is regulated to improve the tracking accuracy, according to the error estimations of Kalman filter. Findings – The innovative ultratightly integrated system could not only enhance the antijamming capability and the dynamic tracking performance of the tracking loops, but also improve the pseudorangerate measurements accuracy for the integrated filter. Originality/value – This paper provides further study on the method of enhancing the carriertracking performance and improving the integration mode in the ultratightly integrated system based on the softwaredefined GPS receiver.