Improving the Performance of the Carrier Tracking Loop for GPS Receivers in Presence of Transient Errors due to PVT Variations

The increase in integration density and the require-ment of low power supplies to reduce energy consumption canmake circuits more and more sensitive to upsets errors. Theloss of robustness increases with process/voltage and temperature(PVT) variations. This paper shows that the impact of errorsthat appear when computing the estimation of the Doppleroffsets in a GPS application can be greatly reduced by tuningappropriately the carrier filter bandwidth. The effectiveness ofthe proposed was proven by comparing the performance a faultyGPS receiver to a non-faulty (noisy-free) GPS receiver at twolevels: the standard deviation of the tracking error variance(by theory and by simulation) as well as the standard deviationbetween positions given by the faulty (noisy) and non-faulty (thenoiseless) GPS receivers. Modifying properly the optimal filterbandwidth values gives astonishing results in terms of robustnessagainst errors. The modification of the bandwidth filter valuesintroduces almost no position degradation in a noise-free GPSreceiver (only11cm in average). With 40 % of error, the standarddeviation of the error in the position does not exceed 2 m byincreasing the PLL bandwidth while the tracking loop does notsupport more than 6% of errors.