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Ugazio S.,Polytechnic University of Turin | Fantino M.,Navigation Laboratory | Lo Presti L.,Polytechnic University of Turin
Institute of Navigation - International Technical Meeting 2011, ITM 2011 | Year: 2011

This paper proposes an algorithm which adapts the Equivalent Noise bandwidth (ENB) of a Digital Phase Lock Loop (DPLL) in real time, with the objective to implement it within a fully software receiver. The algorithm is tailored for Global Navigation satellite System (GNSS) receivers, and can be easily implemented in a fully software platform. The algorithm aim is to reduce the dynamics stress error and the tracking jitter which affect the carrier phase estimate as much as possible. As the dynamic stress error is inversely proportional to the ENB, while the tracking jitter due to the noise is directly proportional to it, a trade-off is needed. This goal is reached by minimizing a cost function, containing the sum of two contributions depending respectively on the input dynamics and on the input noise. In particular the input signal frequency is considered linear, so the input dynamics is related to the input frequency slope. The minimum of the cost function is found by using some simplifications, necessary to achieve a computational speed suitable for real-time adaptation.


Margaria D.,Polytechnic University of Turin | Savasta S.,Polytechnic University of Turin | Dovis F.,Polytechnic University of Turin | Motella B.,Navigation Laboratory
Institute of Navigation - International Technical Meeting 2010, ITM 2010 | Year: 2010

This paper presents an assessment study of the impact of the spreading code properties in the reception of Galileo E1 Open Service (OS) and GPS L1C Multiplexed Binary Offset Carrier (MBOC) signals. The distortion of the discrimination function due to codes cross-correlations properties is analyzed, considering the features of the modulation schemes and investigating also different code families. Simulation results demonstrate that the S-curve of the code synchronization loop can be affected by an asymmetry and a bias in the lock point. Such a distortion can be noticed only in case of receiving a single channel (e.g. the pilot channel), whereas it is not present if the received signal is correlated with a coherent local replica including both data and pilot channels. This effect depends on the code cross-correlation properties and on the receiver setup (reception of data/pilot channels, variable correlators spacing). As a demonstration of its impact on a real single channel receiver, it is also shown that in presence of an interfering signal such a distortion can be magnified and lead to relevant performance degradation.

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