Research On Narrow-band Interference Suppression Techniques For Satellite Navigation Links

In satellite navigation links, when the received signal contain high-power narrow-band interference, the navigation performance will be affected severly. This thesis studies on the narrow-band interference suppression techniques, which enhance the BER performance of the system, thus improving the navigation performance. The main contents of this thesis are as follows:1. A cascade loop of a second-order frequency-locked loop(FLL) and third-order phase-locked loop(PLL) PLL is employed to track the phase of narrow-band interference. Simulation results show that this cascade tracking loop obtains a more accurate phase information compared with the single loop(FLL or PLL).2. An improved least mean square(LMS) algorithm——block least mean square(BLMS) algorithm is adopted. This method can adaptively suppress narrow-band interference. Theoretical analysis and simulation results show that, when the signal to noise ratio(SNR) is from-15 d B to-9d B, this algorithm can guarantee the system to obtain a good interference suppression performance.3. An interference amplitude estimation method is adopted which is suitable for narrow-band interference suppression systems. This method uses a specific structure filter that has a precise estimation of the amplitude dynamic range of narrow-band interference. The results show that, the estimation algorithm can guarantee that the interference magnitude estimated error is less than 1%.4. A narrow-band interference suppression scheme based on interference reconstruction is proposed. For BPSK modulation narrow-band interference, this scheme utilizes the phase information of narrow-band interference obtained by the cascade loop, amplitude information obtained from the amplitude estimation filter and the symbol decision information to accurately reconstruct the interference signal, then, the reconstructed signal is removed from the received signal so that the purpose of suppressing interference is achieved. The simulation results show that the interference suppression scheme get 1d B ~ 3d B SNR gain over the existed interference suppression schemes. Compared with the ideal case, this scheme has about 1d B performance loss. The impact of the scheme on the signal’s phase is minimum.