Design, Implementation and Performance Assessment of Switchable Tracking Loop Filters for Ultra High Dynamic NavIC/GNSS Receiver

Tracking loop design is one of the most important design part of NavIC/GNSS receiver design. The tracking loop determine the dynamics of the receiver. When the high dynamic receiver design is attempted, the noise bandwidth of the tracking loop filter has to be essentially increased for meeting high acceleration and jerk specifications. However the increased bandwidth causes inferior performance in navigation parameters. The stringent accuracy specifications of the receiver may not be met at lower dynamics/near static condition if tracking loop is designed for ultra high dynamics. So a switchable tracking loop is designed which select the noise bandwidth of the tracking loop filter (filter coefficients) from a set of available bandwidth options. When the receiver starts its operations, the filter bandwidth for ultra high dynamics will be chosen as default option. Once first fix is achieved, the receiver dynamics is measured and the tracking loop will be switched to required region of dynamics. Further when the dynamics changes, continuous switching of tracking loop is attempted. The tracking loop with switchable filters are implemented and performance evaluation is completed for different dynamic conditions. The algorithms are originally developed for NavIC receiver, but is applicable for receiver operates for any GNSS constellations including GPS and GALILEO. The design details of third order tracking loop for high dynamic receiver is detailed in this paper along with the design of different filters for meeting the static condition to 25km/s velocity with 20g acceleration and 20g/s jerk. The performance assessment of the the switchable tracking loop at different dynamics (using sky signal and simulated signal using GNSS constellation simulator) is completed and is presented in this paper.