Deep Space Weak High Dynamic Signal Acquisition And Tracking Algorithm And Implementation

The lunar exploration project marks the start of Chinese space exploration into deep space. Differencing from the existing ground based TTC systems, space-based TTC systems, remote sensing ground stations and satellite communications station, deep space TTC systems has its own special characteristics and technical problems.This paper made deep study into the problems of frequency acquisition and tracking. The signals received by the deep space station are often send from other solar system planets, so when reaching the earth the signals are already very weak. Because of the complexity of aircrafts'movement, the frequency of received signal has big Doppler shift. The ultra-narrow-band phase-locked loop structure based on the wiener criteria is discussed, and simulations are made to analysis the performance of the structure.Because of the ultra-narrow-band of the loop, high precise frequency and leap estimation is required. Estimation arithmetic based on periodogram is studied here for single real tone detection in the presence of white Gaussian noise, and the flat effect in frequency estimation problem of high dynamic signals is also investigated. A new method which is also based on periodogram is put forward and analysis is made to assess the performance of it in frequency estimation problem of high dynamic signals.The narrow-band PLL designed is limited to track certain kind of signal, and when the input signal has higher order dynamic, auxiliary frequency tracking arithmetic is needed. The traditional methods such as FLL-based structure can't be used properly to track frequency in the back ground of very low CNR, because of its high threshold effect. A method based on EKF is discussed. The convergence and steady-state error of it is analyzed and a new method of parameter design is put forward.All digital circuit structure of the phase-locked loop and frequency acquisition arithmetic is discussed at the last part of this paper. Several key technologies, as well as the fast frequency acquisition structure which are used in very low CNR background are analyzed. The hardware is accessed through test.