Abstract—Traditional GPS receivers work well when the relative dynamics between the receiver and the satellites are less, i.e., low Doppler and Doppler rate. However, in high dynamic environments the receivers no longer track the signals resulting in the loss-of-lock of GPS position, velocity and time. Typical Doppler range in conventional receiver is ±7 KHz and the Doppler rate is1Hz/s, whereas in high dynamics the Doppler frequency is expected to vary in the ranges ±25KHz with Doppler rates of about 100Hz/s. Therefore, it is a challenging task to develop algorithms to receive signals under high dynamics. To solve this problem, a new frequency-locked loop (FLL) assisted phase-locked loop (PLL) technique of higher order is introduced in this paper. Second order FLL reduces the locking time by frequency pulling and thus rectifies the higher dynamic frequency errors at the receiver and allows the third order PLL to lock on to the dynamically changing phase of the signal with high accuracy. The proposed algorithm was implemented using Matlab/Simulink and evaluated by simulated data sets. Results show that the proposed algorithm of using higher order frequency loop has improved performance when the input signal changes comprise large dynamics.
Index Terms—Baseband processor, GPS, high dynamics, higher order loop.
Sidhant Kumar Tiwari is currently working with L&T Infotech as a Software Engineer in the J2EE domain. (E-mail id: sidhanttiwari@yahoo.com)
Cite: Sidhant Kumar Tiwari, Swarna Ravindra Babu and R Kumar, "Design Of baseband Processor for High Dynamic GPS Signals Using Higher Order Loops," International Journal of Machine Learning and Computing vol. 1, no. 5, pp. 516-521, 2011.