Research And Realization On Acquisition Technique Of DS/FH Hybrid Spread Spectrum Signal For Deep-space TT&C

Deep-space tracking, telecmetering&command (TT&C) and communicationsystem is the most important part of the information security system in the deep-spaceexploration activities, to further enhance the anti-jamming performance of the system,DS/FH hybrid spread spectrum has become the development trend in the future, as thebasic problem of the establish communication, the directly acquisition of DS/FH spreadspectrum signal is the precondition whether the system can practical application.However, put DS/FH spread spectrum technology into deep-space TT&C system,it will lead some new and higher challenges for the research of signal acquisitiontechnology:(1) Deep-space communication has long-distance and harsh channel, resulting in aweak reception and large timing errors;(2) The TT&C targets has high dynamic characteristics, so the Doppler effect ofthe received signal is obviously;(3) TT&C operations requiring high precision, so select chaotic sequence whichhas no cycle and improve the chips rate, it will increase the difficulty of acquisition.This thesis studied the signal acquisition technology of DS/FH TT&C system indeep-space, including:First, for the specific scenes in deep-space TT&C, we discuss and quantify theimpact of its specificity to the signal acquisition. Consider the farthest communicationdistance is4108km, the vehicle speed is12km/s, and combined with the downlinkbudget, we analysis the signal-to-noise ratio (SNR) of the received signal, the timeuncertainty, the Doppler rate and so on, the period of DS/FH hybrid spread spectrumpseudo-code is15years.Secondly, in the constraints of search range and acquisition time, a detailed designscheme is given. Based on the segmentation of Doppler frequency and large-scaleparallel, we give a multi-channel search strategy, it has10channels, each channel with100-channel parallel correlator, for the signal with100kHz Doppler shift and500,000chips uncertainty phase, it can be succeed catch in20s.Third, in the constraints of carrier-to-noise ratio, the integration strategy of jointdetection with coherence and non-coherent is given. We studied the algorithm ofcoherent integration and non-coherent integration, include the gain of SNR and theconstraints of integration time, we can get39dB SNR by use500s coherent and2msnon-coherent integration.Fourth, joint the development of deep-space TT&C system’s equipment, wecomplete the achieve validation of the acquisition scheme. Used FPGA as the achieve device, a detailed design of processing algorithms and implementation processes isgiven. Under the test conditions, the probability of success is greater than90%, theaverage acquisition time is less than20s, meet design specifications.The research results above not only enrich the DS/FH spread spectrum signalacquisition technology in deep space TT&C, but also provides the theoretical andmethodological support, the research has been engineering verification, it can be appliedto the next-generation hybrid spread spectrum system.