Research On FPGA-based Pseudolite Navigation Signal Cover Communication And Interference Cancellation

With the GPS widely used in various fields, we pay more and more attention on the study ofsatellite navigation signals jamming technology. Sometimes the intentional or unintentionalinterference of satellite navigation signal is disastrous, although the use of decorrelation can reducesuch interference, but it’s difficult to solve the interference problem effectively because the carrierfrequency and the spatial spread of the satellite navigation signal are public. This paper presents amethod to realize the cover overlapping communication of pseudolite navigation signal by usingcommunication signal as a cover and superimposing pseudolite navigation signal over thecommunication signal.The overall structure and hardware solution of pseudolite navigation signal cover communicationand interference cancellation experiment based on FPGA is given. It contains communication signaltransmission unit, pseudolite navigation signal transmission unit and cover overlapping signalseparating unit. Also it specifically introduces the modulation scheme and spreading code ofcommunication signal, the C/A code generation, USB interface design and IF signal processing ofpseudolite navigation signal, the synthesis scheme of communication signal and pseudolite navigationsignal. It analyzes the interference cancellation separation algorithm of cover overlapping signal.Costas loop and the lead/lag doors are used to achieve carrier synchronization, code synchronizationand the demodulation of communication signal. Then it estimates the Doppler shift, the phase offsetand the code biased of communication signal, reconstructs communication signal, and realizes theseparation of communication signal and pseudolite navigation signal.Communication signal transmission, pseudolite navigation signal transmission and coveroverlapping communication separation are respectively tested over FPGA. Communication signaltransmission unit contains the carrier NCO and code NCO over FPGA simulation test, and it’s verifiedby a spectrum analyzer. Pseudolite navigation signal transmission unit contains the firmware of USBdata interface test and the interpolation filter design over FPGA simulation test, and it’s verified bysoftware receiver. Cover overlapping signal separating unit contains the complex phase rotation, CICfilter, Costas loop and signal separation algorithm over FPGA simulation test.