Behavior of the GPS Timing Receivers in the Presence of Interference

GPS timing receivers have been used for synchronizing telecommunications equipment since the early 90’s, currently providing an accuracy of up to 10ns. Such a high requirement of accuracy demands excellent operation from GPS timing receivers, avoiding the degradation of the synchronization process. Interference is an important threat to GPS performance. Such harmful interfering signals can originate from any electromagnetic radiation source producing its main signals or their harmonics in GPS bands. These sources may include signals from UHF/VHF TV transmissions, FM transmissions and VOR/ILS services. Any degradation in performance, due to introduction of interference can cause these receivers to provide a low quality timing solution, or to lose lock with incoming GPS signals altogether. This consideration motivates the study of the performance of GPS timing receivers in the presence of harmful interference. This paper proposes a hypothesis about interference effects on GPS timing receivers, and then confirms the hypothesis with experimental results. It also provides reasoning to explain this behavior of GPS receivers and identifies areas for further investigation.