Abstract:

In order to reduce the calculation load of a carrier tracking loop in a Global Positioning System (GPS) receiver, an improved discriminator algorithm based on four-quadrant arctangent function is proposed, which is shared by Phase-Locked Loop (PLL) and Frequency-Locked Loop (FLL) discriminators. The PLL discriminator is insensitive to the navigation message data. The FLL discriminator overcomes the frequency uncertainty by the shared four-quadrant arctangent function unit as well as correction functions. Furthermore, parameter setting of the discriminator algorithm is investigated with additive white Gaussian noise at various signal-to-noise ratios. Theoretical analysis comparison and simulation show that the improved algorithm not only has good discrimination capacity with the carrier phase and frequency, but also has the characteristics of small calculation load and low complexity. Therefore, carrier tracking loops can improve operational speed and occupy less system resources.

Key words: information processing technology, discriminator, phase-locked loop (PLL), frequency-locked loop (FLL), fourquadrant arctangent function