Design And Implementation Of Variable-code-rate Inter-satellite Communication System Based On Pico-Nano Satellite Formation

With the rapid development of the Pico-Nano satellite technology,the formation system of Pico-Nano satellite has become a hotspot in modern satellite area.Inter-satellite communication,as the premise and foundation of satellite formation cooperation,undertakes data transmission tasks such as control instructions and payloads.Inter-satellite communication links in satellite formation have time-varying characteristics.Fixed communication rate will restrict system efficiency.Therefore,it has a practical meaning to develop a variable rate inter-satellite communication system suitable for the formation of Pico-Nano satellites.Firstly,this paper compares the domestic research of inter-satellite communication and variable rate communication with the abroad.Then,completes the design of variable code rate inter-satellite communication system which meets the project requirement based on miniaturization and software radio.The final design of the inter-satellite communication system has the advantages of the concept of modular and adaptive,which meets the needs of Pico-Nano satellite formation application.The research contributions of this paper are as follows:(1)According to the application requirements of inter-satellite communication system,the characteristics of inter-satellite links are analyzed.The transmission and reception scheme of the whole variable code rate communication system is analyzed and designed.The design of multi-rate digital processing module based on FPGA is determined.(2)For mutil-rate transmission requirements,a cascade structure of coefficiently overloaded square root raised cosine filter and multi-rate interpolation is studied and designed.which can meet the transmission requirement and reduce the resource consumption of the system.(3)Aiming at the demand of mutil-rate receiving requirements,multi-rate decimation module,multi-rate synchronization module and signal-to-noise ratio estimation algorithm arc designed respectively.Multi-rate decimation module realizes the reduction of sampling rate for different bit-rate signals.Multi-rate synchronization module realizes synchronization of download wave and symbol at different signal rates.Design and implementation of SNR estimation algorithms.and FPGA simulation results show the estimation error is less than 1 dB.(4)The hardware test platform is built to test the transmission and transmission system of variable speed digital IF.The system communication rate range is 2kbps to 5Mbps;the first sideband rejection of baseband spectrum is 35 dB;Multi-rate module works reliably in rate switching;receiver sensitivity is-122.5dBm.In summary,the variable code rate inter-satellite communication system designed in this paper can meet the inter-satellite data transmission requirements;as the same time,it has the characteristics of the concept of modular and adaptive.