On The Application Of Adaptive Technique In Navigation Receiver

Interference environment in which satellite navigation receiver is unknown and varies with time, the receiver must have a certain environment adaptability, to eliminate the interference signal capture. It is typically to combine the technology of adaptive and antenna array in satellite navigation receiver. This offers the receiver spatial ability to solve signals. And then adjust the weighting factor of antenna array in real time using adaptive algorithm which according to the signal environment. A certain gain in signal in the expected direction and a zero notch in the jamming direction are formed respectively. For the research of navigation receiver jamming algorithm and its implementation on FPGA applying to dynamic environments, three following works were performing.(1)Quantity analyzed the anti-jamming ability of spatial adaptive antenna array in white noise and colored noise, respectively. The result is, in a system with M antennas array, SNR are improved to 10 log(M) in Gaussian white noise. Under the conditions that the angle of signal arrival are known, the statistical properties of signal and jamming are ideal, the improvement of SNR in colored noise is comparable to its in Gaussian white noise. This shows adaptive beam forming can effectively eliminate jamming. But in practice, sample covariance are usually used to approximate the true covariance, the degree of improvement is decreased.(2)Evaluated the performance of power inversion(PI) of space-time beam forming. The result is space-time PI algorithm can effectively eliminate the coexistence of the multiple interference in complex environments. But by simple constraints affected, signal to interference and noise ratio severe attenuated when the jamming approaches to signal. Studied the closed loop adaptive weight vector calculation method. An improved LMS algorithm, SM-NPI algorithm, was applied to the updating of weight vector of the space-time PI beam forming. Simulation results show that SM-NPI can effectively improve the convergence speed on the basis of keeping the LMS algorithm with small computation characteristics. To further improve the convergence speed, multi-stage Wiener filter method, a kind of beam forming algorithm for open loop, was studied. In order to solve the computation problems of Wiener filter matrix, a dimension reduction method was discussed. Simulation results show that the multistage Wiener filtering method can reduce matrix dimension while meeting the filter performance. Moreover, the computing speed further improved.(3)Researched the implementation in FPGA of adaptive algorithm. For the defects of LMS algorithm, the filtering error calculation and the weight updating must be in order, D-SM-NPI, a weight algorithm based on space-time power inversion criterion which can be realized in FPGA were proposed. This algorithm used the parallel of LMS which were implemented by the delay least mean square(DLMS) combined with SM-NPI weight update method. ModelSim simulation and hardware testing show that the anti-interference algorithm designed in this paper is able to capture the satellite signal in the suppression of interference noise environment...