Research On The Acquisition And Tracking Of The High Dynamic TT&C Signal In Near Space

Near space, which is a route human must pass through to reach the outer space，isan important strategic space. The TT&C communication system is a core technique forinformation security of the aircraft，while the key for efficient and reliable working ofTT&C communication system is to realize the fast acquisition and tracking of the highdynamic TT&C signal. In this article, we will make an analysis of the channelcharacteristic and the model of channels in the near space. According to the highdynamic characteristic of the near space aircraft, we then focus on acquisition andtracking of TT&C signal and make deep research on them.Firstly，this article makes an analysis of the transmission characteristics of TT&Ccommunication system with lower elevation in near space. With the establishment ofcommunication channel of TT&C system, e.g., Multipath delay spectrum model andDoppler power spectrum model, the channel model is simulated. Secondly, a detailedintroduction and simulation of the traditional method of acquiring the spread-spectrumsignal is given. Based on the characteristic of high dynamic in near space, a fast codeacquisition algorithm using FFT is introduced. The feasibility and advantages of ouralgorithm is shown according to the results of the simulation. Finally, we make aresearch on the code tracking and carrier tracking of the spread spectrum signal.Simulation of our method is realized by Matlab, in which DLL is used for code trackingand a composition of CPAFC and Costas loop is used for the carrier tracking loop. Theresults of the simulation show that we can acquire the signal even in a high dynamicchannel.