Research On PN Code Acquisition Technique In Unified Spread Spectrum TT&C System With Large Dynamic Range Doppler Frequency Shift

With the rapid development of telemetry tracking and control (TT&C), thepopular unified S-band TT&C system have many defects. Hence, we need a newTT&C system. Unified spread spectrum TT&C system use spread spectrumtechnology for overcome the shortcomings of the USB TT&C system effectively.In the procedure of space telemetry, the high speed of the aircraft caused largeDoppler frequency shift. And the large Doppler frequency shift has a negativeimpact on signal demodulation and PN code acquisition function. And it will makedifficult to capture the signal. So in this dissertation, a suitable plan for PN codeacquisition in the unified spread spectrum TT&C system with large dynamic rangeDoppler frequency shift is being on researched.First of all, this dissertation analyzes the characteristics of high dynamiccooperation objective’s PN code acquisition and shows the definition of highdynamic range. Using traditional sliding correlation detection to analyzes theimpact of the Doppler shift created by the cooperation objective. Based on theanalysis, dissertation uses FFT-based PN code acquisition method to analyze thespectrum of the signal and estimate the Doppler shift.Secondly, we can analyze the impact of the Doppler shift with the prioriknowledge supplied by cooperation objective in the telemetry tracking. In thisdissertation, we use the FFT-based PN code acquisition method. This programuses the FFT to analyze synchronization signal’s spectrum and complete the PNcode acquisition after remove the Doppler shift.Finally, this dissertation analyzes the characteristics of high-dynamicnon-cooperative objective in the telemetry tracking and defines the first-ordercorrelation function of the PN code in high dynamic conditions, and shows thesecond-order correlation function trends. The Doppler shift has a serious impacton Non-cooperative objective PN code acquisition. Because loss of the PN codecorrelation function, we improve the FFT-based PN code acquisition method tosearch the Doppler shift twice times. In the first time we use lower indicators forthe estimation of the Doppler shift. In the second time we increase the indicatorsand search for the phase. Finally, complete the task of the PN code acquisition.