Research On Anti-jamming Algorithms Basedon STAP For GPS Receiver

With the navigation receiver has been widely used in national life and military actions,the performance of the receiver also is proposed more sophisticated requirements. Especially in military strikes the electromagnetic environment is constantly changing, a reliable receiver must be able to accurately respond to this changing environment, so the research on interference suppressing need more extensive and in-depth. The paper majors in the space-time adaptive processing algorithm.Space filter to suppress the interference is directly related to the number of array antenna,also its degree of freedom is smaller, the ability of suppressing wideband and multipath signal is not very good. Space-time interference suppressing combines the advantages of space filter and time filter, so it can suppress jamming signal especially wideband. While in the case of the system without increasing the array elements, the degree of freedom is greatly increased,suppressing ability is improved, and this approach is more suitable for system upgrades and improvements. In this paper, the main results are:(1) Firstly, the dissertation analyz the signal characteristics, set up signal model. The GPS signal model and characteristics was proposed. Typical interference is analyzed, and then the mathematical model of pressing type interference is set up.(2) The basic theory is dicussed. The array signal model and the relationship between input and output are established; mechanism and algorithm of STAP are expounded; optimal criterions and the relationship of them are analyzed; the impacted by number of antennas,delay of time and angles of interference is expressed; the distortion of GPS signals induced by STAP is proposed.(3) As the anti-jamming capability improvement through STAP, the computational complexity increases greatly. In order to reduce the calculation the reduced-rank simplification method is one of the key techniques in this paper. Principal Components (PC)and Cross Spectral Metric (CSM) are briefly proposed, and Multistage Nested Wiener Filter(MWF) is study in a deep-going way. The forward decomposition is replaced by correlation subtractive architecture(CSA) and made some improvements. And then a simplification iterative algorithm, without recalculating all the elements, is proposed for selecting rank in comprehensive. Finally, the proposed method is called simplified-MWF. Through digital simulation, this method is proved got good reduction performance, convergence and robustness.(4) To improve robustness in finite snapshot condition is an important part of this paper.Finite snapshot condition can lead to adaptive pattern distortion, waveform distortion and high sidelobe, performance of STAP is caused worse by those issues. An adaptive method to determine the diagonal loading value is proposed for finite snapshot condition. The method based on fixed value loading, uses the covariance matrix and utilize adaptive weight vector of sampled signal to select diagonal loading value. Therefore, the filter is more suitable for changing interference environment. The simulation results obtained very good sound effect.for this situation presents an adaptive diagonal loading method based on a fixed value loaded on the use of data the adaptive quantity,more the simulation results achieved good sound effects.