Noncoherent Code Discriminator Gains for Global Navigation Satellite System Signal Tracking

Ryan S. Cassel

Peer Reviewed

Abstract: Many common discriminators used for code tracking of global navigation satellite system (GNSS) signals are ratios of quadratic forms of the correlation outputs. Here we derive a general expression for the gain of this type of discriminator and show that it depends on the effective carrier-to-noise ratio. We then evaluate this expression for several different code discriminators and GNSS signals, including GPS C/A-code, P-code, L1C, and M-code, Galileo E1 OS, GLONASS L1OF and L2OF, and BeiDou B1I and B2I. We also determine how noise and interference saturate the discriminator (i.e., make its output less sensitive to changes in the input) and the resulting effect on loop bandwidth. The discriminator gains described in this paper compensate for the saturation and ensure that loop bandwidth and code tracking performance can be accurately predicted and controlled over a critical range of effective carrier-to-noise ratios.
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