Jamming of Global Navigation Satellite Systems (GNSS) is now a major thread for its users. A jammed receiver will lose its fix at a certain distance and won’t be able to provide position, navigation and timing (PNT) information. At larger distances there will be a fix to provide this PNT information, however the information will be less accurate as the carrier to noise (C/N) ratios of the received signals will be suppressed by the jammer. In this paper the (pseudorange) accuracy of a GNSS receiver under jamming is investigated in order to provide more insight into the effects of a jammer on the accuracy of a GNSS receiver. The theory as found in literature will be reviewed after which this theory will be evaluated by comparing theoretical results with actual measurements using a high-end GNSS signal simulator and a GNSS receiver.

The impact of a jammer on the delay lock loop (DLL) accuracy is primarily depending on the type of jammer signal, C/N and modulation of the received signal, and the DLL architecture (correlator spacing, bandwidth, etc.). As the C/N is the primary parameter that is influenced by the jammer, the focus lies on the relation between the jammer power and the C/N. Two different signal modulations are chosen for the analysis, first binary phase shift keying (BPSK) as used by GPS C/A, and second the (Composite) Binary Offset Carrier ((C)BOC) as used by Galileo E1. In theory the BOC code should be less affected by a jammer. In order to have full knowledge and control over the DLL architecture an open source software defined receiver, in this case GNSS-SDR, is used.