Detection And Mitigation Techniques Of Pulsed Interference And Narrowband Interference,and The Compound

The extreme weakness of satellite navigation signal make it vulnerable to a variety of in-band and adjacent band interference.Pulsed interference and narrowband interference(NBI),and the compoud are the common accidental interference pattern for global navigation satellite system(GNSS).Thus,the detection and mitigation techniques of pulsed interference and NBI,and the compound are important issues for both theoretical and engineering significance.Motivated by these challenges for satellite navigation signal monitoring receivers,the thesis presents an extensive theoretic and experimental investigation on parameter estimation of pulsed interference,pulsed interference mitigation,and the pulsed and narrowband mixed interference mitigation.The main work and innovative achievements can be summarized as follows.First,a novel biased block-flow noise power estimation algorithm is proposed for pulsed interference detection and mitigation.Based on block-to-block iterative mode rather than inter-block interative mode in backward consecutive mean excision(BCME)algorithm,the proposed algorithm is relatively low-cost when compared to the BCME algorithm.Subsequently,the relationship between the estimated noise power and the threshold parameter is also illustrated in virtue of the probability theory.Analytical and numerical results show that the algorithm can converge fast when the background noise power changes,and the estimated value of the noise power after convergence reaches about 95% of the true value when the threshold parameters is set as 4.6(corresponding to 1% probability of false alarm and signal-to-noise ratio(SNR)loss is negligible).Second,a low-complexity duty cycle estimation algorithm for pulsed interference is presented to resolve the conflict between estimation accuracy and computational complexity of popular algorithms.The algorithm combines the BCME or forward CME(FCME)alogrithm with accumulation of binary values to reduce the probability of false alarm and improve estimation accuracy while the increased amount of calculation can be ignored.Numerical results show that the estimation accuracy of the proposed algorithm is comparable with the localization algorithm based on double-thresholding with ajacent cluster combining(LAD-ACC)while the computational complexity can be reduced to the half of the latter at least.Third,the analytical expression is derived for the effects of pulse blanking(PB)algorithm on GNSS receivers due to lack of theoretically predicting results based on the Gaussian broadband pulsed interference model and the definition of SNR.Subsequently,the optimal thresholds can be achieved with given interferential conditions,which provide theoretical guidance for threshold parameter settings.Analytical and numerical results show that all the threshold-crossing samples should be blanked rather than preserved for Gaussian broadband pulsed interference with duty cycle less than 20% and power larger than 0d B,and then a minimum SNR loss can be ensured.Finally,a minimum energy block algorithm is proposed to combat the pusled and narrowband mixed interference due to that it is difficult to cope with the mixed interference effectively by the feasible simple combination with the conventional frequency-domain blanking(FDB)and time-domain blanking(TDB)techniques.The proposed algorithm segments inputs into blocks and groups consecutive blocks into batches,and chooses these minimum energy blocks in all batches,which are assumed to be not contaminated by pulsed interference,to estimate the power spectrum density(PSD)of NBI.Ultimately,the mixed interference can be suppressed by the FDB and TDB techniques in serial.Numerical results show that when the Gaussian NBI's interference-to-noise ratio(INR)is fixed at 10 d B and the INR of Gaussian broadband pulsed interference with fixed duty cycle of 10% is greater than or equal to 10 d B,the correct detection probability of the propose algorithm is greater than 98%.In addition,the proposed algorithm outperforms the two types of simple combination of conventional pulsed interference and narrowband interference suppression algorithm,and achieves a mitigation loss close to the ideal mitigation loss value under the three given harsh mixed interference scenarios.The main results of this thesis have been used in China's own satellite navigation signal monitoring receivers.