Navigation Receiver Interference Suppression Algorithm And Performance Simulation

The Global Satellite Navigation and Positioning System, which has been developed by the DOD since the 20th century 1970s, as for the continually application and perfecting during the recent 30 years, nowadays this System has already been able to provide all-weather services such as high definition navigation, positioning and timing etc. in worldwide areas. Just for the powerful functions possessing by the GPS system, make it obtaining more and more widely application. Especially in the modern information-based wars, the one who is able to use the GPS system effectively, while can prevent the enemy using GPS simultaneously, is capable of taking absolutely advantages in the battle field through the high definition and high dynamic real-time positioning ability.However, because of the inherent characteristics of the GPS system, the receiving signals come from the sky thousands of miles away, while by the power restriction of the signals emitting by the GPS satellites, the arriving satellite navigation signals into the ground are very weak, such weak signals can easily been affected by both accidental and intentional jamming signals at the GPS receivers. In the condition of existing jamming signals, the time for the receiver capturing the navigation signals will be extended, indeed, the capture process will be failure. Thus, in order to make the GPS receivers working normally in the terrible electromagnetism jamming signal environment, we must first do the suppressing or decreasing jamming signals operation toward the receiving GPS signals to make sure the satellite navigation communication is able to synchronize reliably and accurately in the intense jamming condition. In this paper we mainly discuss two methods of suppressing the intense jamming signals toward the GPS navigation signals, one method is based on the subspace projection of the array signals, and another is based on the Short Time Fourier Transform(STFT).The jamming suppression algorithm based on the Subspace Projection: It is assumed that the GPS signal and interference and noise are independent, first we decompose the covariance matrix of the signal received by the array antennas, calculating the subspace array corresponding to the interference, on this basis, we calculate the orthogonal subspace of the jamming signals, thus we multiply this orthogonal subspace to the receiving signal array vectors to eliminate jamming signal. Furthermore, we weigh the signal processed by the subspace projection through the maximum signal-to-noise ratio coefficients, finally we do the acquisition procedure.The jamming suppression algorithm based on the STFT: We design this GPS anti-jamming algorithm according to the time and frequency separating characteristic toward the non-stationary signals of the STFT transform. The simulation test results indicate: we are be able to capture the satellite navigation signals after the anti jamming processing toward the narrow width jamming signal (SJR=-50dB) and the linear frequency modulation (LFM) jamming signal (SJR=-40dB), by the same time, we can estimate the Doppler frequency shift of the carrier wave accurately.