Research On Frequency Estimation In High Dynamic Environments Based On Adaptive Convex Combination Algorithm

With the rapid development of defense technology, accurately striking weaponsgradually become to be high-speed, penetration ability and attack fargoing. Because of thehighly dynamic environment, larger Doppler shift of the signal is produced, and it may reachthousands of Hertz. In order to make sure that the usual carrier locked loop is locked, thebandwidth of the loop filter must be increased, then, it will bring in more broadband noise,when the noise level increases to more than loop threshold, it will result in the carrier trackingloop to lose lock, once it happens, the estimated value of distance and its rate of change willbe lost. Without increasing the carrier PLL loop bandwidth, the carrier capture zone of theDoppler shift is often more than the carrier phase-locked loop, it can not guarantee continuousand reliable acquisition and tracking. Above all, how to rapidly estimate the Dopplerfrequency in the high dynamic environment is an urgent need to satellite navigation receiver.The paper will study for above problems.Firstly, the composition of the GPS signal and the works elements of GPS receiver isintroduced in this paper. And it also focuses on the analysis of the tracking loop of GPS signal.Then, in high dynamic environment, this paper makes an detail analysis of the Doppler shiftimpact on the tracking loop of the carrier, basis on which, we also analyse the limitations ofthe traditional phase-locked loop and frequency-locked loop tracking method in high dynamicenvironment. In order to overcome the shortcomings of traditional methods, someacademicians advanced some proposals to resolve tracking problem in high dynamicenvironment, such as joining the phase-locked loop and frequency-locked loop together orextended Kalman filter algorithm. The paper makes details analysis of these two methodsapplying in high dynamic environment, and it also points out their shortages.In regard to this, this paper utilizes the convex combination of adaptive filter to solvecarrier tracking problem in high dynamic environments. Firstly, it makes details analysis ofthe fundamental principles of the adaptive convex combined fiter. Then, it introduces somekinds of this algorithm’s performance. And an improved convex combination method isproposed to enhance its performances. The paper particular discusses the principles of theconvex combination of adaptive filter in the application of frequency estimation, andnecessary simulation results are given. Finally, the method is introduced into the Dopplerfrequency estimation in the high dynamic environments; the computer simulation resultsshow that the method is feasible.