Research On Key Technology Of Satellite TT&C Data Transmission Integrated Machine

With the continuous progress of China’s aerospace industry,especially the opening of commercial aerospace field,micro-nano satellites have entered the stage of vigorous development.Under the strict constraints of volume,weight and power consumption,it is an important countermeasure to combine the measurement and control and data transmission equipment of conventional satellites into one to reduce the total weight of the equipment.The integrated system of measurement,control and data transmission not only has high speed data transmission,but also has the ability of ranging and positioning similar to conventional measurement and control equipment.Firstly,the acquisition basis of spread spectrum signal is introduced,and AOS protocol and range measurement method classification are briefly introduced.On this basis,the problems of acquisition of spread spectrum signal in high dynamic environment and the combination of on-board measurement and control and data transmission into integrated channel are analyzed in detail.The main research contents of this paper are as follows:(1)The influence of code Doppler on correlation peak.The correlation attenuation between the input PN code with the Doppler effect and the local PN code in the acquisition of the spread spectrum received signal is analyzed.The expressions of correlation peak attenuation of input PN code and local PN code are calculated when they are aligned at intermediate time,initial time and any time,and the simulation results are given.Finally,it is demonstrated that middle time alignment brings the least attenuation on the correlation peck,and the head or tail alignment bring the largest attenuation.(2)Based on the above results,the time-domain serial acquisition algorithm is improved.In the high dynamic environment,the Doppler frequency shift will bring about the inconsistency between the local PN code and the input PN code,which will lead to the low accuracy of the acquired PN code and the drift between the phase of the acquired PN code and the phase of the output PN code.An improved time-domain serial acquisition algorithm is proposed,which updates the local PN code according to the search frequency and corrects the phase by secondary acquisition.(3)Adaptive AOS scheduling algorithm.In the satellite downlink,the ranging pseudo code,telemetry data and remote sensing data are transmitted through one channel.The design scheme is that the ranging pseudo code,telemetry data and remote sensing data are respectively transmitted through the insertion service,multiplexing service and bit stream service,and the virtual channel is scheduled.According to the real-time and priority requirements of each data,the adaptive scheduling algorithm is used to adjust their weight and allocate the physical channel reasonably.At the same time,the channel utilization is improved.