Satellite Navigation Receiver Time-frequency Interference Suppression Algorithm Research

The pattern of the future war will be "digital war" which is on basis of the high-tech, and the advanced navigation and positioning technology is an important guarantee to it. As a universal positioning system, GPS which has unexampled superiority of all-functional,global and all-weather to other navigation devices has aroused more and more people's attention. So it`s not only important to make researches on jamming technology to prevent the navigation device of other side from working, but it's also important to make researches on advanced anti-jamming technology to adapt to the requirement of the modern information war, which has significant meaning to promoting the performance of modernization weapons, even to enhancing the whole martial effectiveness. This dissertation is focused on the study of anti-jamming technology of GPS receiver.GPS system is based on the spread spectrum system in which the anti-jamming ability is an essential factor. This ability has effect on the performace of whole system, so it`s necessary to take the anti-jamming measures in GPS receiver. In recent years, the anti-jamming technology of spread spectrum is always the hot point of the anti-jamming research area. Especially, the anti-jamming technology for narrow-band jamming has already been researched for a long time, and the classical method of filter is to use window and shading disposal in time or frequency domain. But for broad-band jamming, the Pseudo Noise Code and Noise signal has the characteristic of strong time-frequency coupling which make it difficult to separate the jamming from our desirable part by classical method of filter.This dissertation is mainly focused on the study of anti-jamming technology basic on time-frequency method. In the dissertation, we first analysed the effect on the correlation output of C/A code by joining the ContinuousWave (CW),Multi- ContinuousWave and Linear Frequency Modulate (LFM) jamming signal separately. And we also analysed the degree of effect on the Bit Error Rate (BER) of GPS receiver from CW,MCW and LFM jamming of different Signal to Jamming Rate (SJR) by using Monte Carlo model. Then we introduce the time-frequency theory and time-frequency transform which is foucs on the Short Time Fourier Transform (STFT) and Fractional Fourier Transform (FRFT). We put forward the scheme of jamming suppression based on STFT via time-frequency domain,scheme of jamming suppression based on FRFT via frequency domain,scheme of LFM jamming subtracting based on FRFT via time domain, and established the algorithms corresponding to schemes to achieve jamming excision in GPS receive signals. At last we maked some simulations of the established algorithms by using Matlab simulation software to prove its feasibility and thevalidity. And it has resulted that the algorithms are useful to jamming excision in GPS receive signals. By analyzing the results of simulation, it indicated that receiving signal would be distorted by using the algorithm based on STFT via time-frequency domain because of the conflicting between time bandwidth and frequency bandwidth of STFT. And the algorithm of LFM jamming subtracting based on FRFT via time domain could only applied in the situation that there is only one LFM jamming exsiting. The algorithm based on FRFT via frequency domain is more complex than the other two algorithms, but it works better.