Key Techniques Of Small Satellite Communication Systems

In recent years, small satellite communication systems has been widely researched andapplicated, because of its advantages, such as, light-weight, low cost of development and launch, widesignal coverage, stable performance, etc. Small satellite communication systems has become apowerful supplement for large synchronous orbit satellite communication systems and got theattention of domestic and international research institutions. So the research of small satellitecommunication technology has important theoretical and practical significance.The link budget method of small satellite communication systems, the blind parameter estimationestimation algorithms based on signal cyclostationarity, as well as the timing and carriersynchronization algorithms are studied in this paper.The limited size of small satellite, limited space-borne transmitter power, long wirelesstransmission distance and large interference and noise are full considered in the link budget of thesmall satellite communication systems. The uplink and downlink of the small satellite communicationsystems is respectively analyzed.The blind estimation of the signal parameters is the important premise of satellite communicationinvestigation and inspection. The carrier frequency estimation with improved multi-frequencyestimation algorithm and the code rate estimation based on the cyclostationarity of the satellite signalsare studied. The feasibility of the algorithms has been analyzed through the simulation of BPSK,QPSK, SOQPSK signals on Matlab. The algorithms can deal with low SNR signals, and have a goodadaptability for the characteristic of limited power and large attenuation of the satellitecommunications.The symbol-before-carrier synchronization algorithm is studied on account of the Doppler andnoise affection in satellite communications. The symbol synchronization is realized with the feedbackloop based on interpolation and the carrier synchronization with second order decision-feedback loop.Data processing of the algorithm is relatively fast as it is mainly in a period of Symbol time, andresources are saved with no preamble. The algorithm was proved to be very practical in satellitecommunication systems for its large capture range and good BER performance in the simulations.Finally，the simulation of the communication system is achived on hardware platform. Thevalidity of the algorithm is verified by programing with verilog lauguage and testing on the XilinxVIRTEX-5developping board.