Design of Second and Third Order PLLs with Adaptive Bandwidth in Real Time

摘要

This paper proposes an algorithm which adapts thernEquivalent Noise bandwidth (ENB) of a Digital PhasernLock Loop (DPLL) in real time, with the objective tornimplement it within a fully software receiver. Thernalgorithm is tailored for Global Navigation satelliternSystem (GNSS) receivers, and can be easily implementedrnin a fully software platform. The algorithm aim is tornreduce the dynamics stress error and the tracking jitterrnwhich affect the carrier phase estimate as much asrnpossible. As the dynamic stress error is inverselyrnproportional to the ENB, while the tracking jitter due tornthe noise is directly proportional to it, a trade-off isrnneeded. This goal is reached by minimizing a costrnfunction, containing the sum of two contributionsrndepending respectively on the input dynamics and on therninput noise. In particular the input signal frequency isrnconsidered linear, so the input dynamics is related to therninput frequency slope. The minimum of the cost functionrnis found by using some simplifications, necessary tornachieve a computational speed suitable for real-timernadaptation.