Characterization of Non-Stationary Interference Signals in GNSS Applications

Nowadays, also thanks to the modernization of the Global Navigation Satellite Systems (GNSS), the number of applications based on the user position is increasing very quickly. Since for many of those applications the accuracy level is one of the core requirements, the monitoring of the interference produced by other telecommunication systems has a fundamental role in the design of GNSS receivers. In fact, because of the useful signal reaches the receiver antenna characterized by a very low power level, the interference from other electromagnetic sources can become one of the main causes of the signal degradation. Moreover it is well known that the frequency spectrum appears very busy and the characteristics of the signals that can interfere with the GNSS one are very different from each other.1 For this reason the algorithms able to detect or mitigate the effect of an interference should be precisely designed for each different interference source. The presented technique is suitable for non-stationary signals and it develops into two different steps: the detection of the presence of the interference and the characterization of it. During the second phase the technique is able to estimate the time and frequency characteristics of the undesired source. The algorithm is based on the analysis of the auto-correlation function of the received signal, which is composed by the GNSS signal, the noise and the interference, and it exploits the particular characteristics of the auto-correlation of the noise and of the GNSS signals. In the paper the performance of the algorithm are shown for its application to pulsed signals. Moreover the paper shows the benefits obtained by introducing an algorithm based on the modal analysis during the detection phase.