Satellite Emergency Communication System Baseband Design Of S-band Low Information Rate

Emergency communication is a communication means and mechanism of a group with various communication methods,and to meet the special communication requirements for emergencies such as natural or man-made.Satellite communications has been essential to the field of communication technology,its technical characteristics was very suitable for the requirement of emergency communication system.However,due to the limited power of satellite transponder,making satellite communication systems typically use surface antenna,resulting in a large volume of equipment,inconvenient to carry.In addition,L/C-band frequency resources is growing increasingly tense,the S-band resources are becoming more and more abundant.Therefore,in the background of satisfied the requirement of disaster relief and other emergencies of emergency communication,monitoring and measurement data back,the S-band satellite emergency communication system with low rate of information was explored and studied,in order to solve the problem of communication in special scenario.First of all,the research status of emergency communication is analyzed in detail,the requirement of satellite communication in emergency communications and other special application scenarios is introduced,also some common satellite communication system and its developing direction is introduced.Secondly,the feasibility of constructing the emergency communication system with low rate of information on S-band is demonstrated,the division of S-band and the use conditions are analyzed and discussed,the transmission links and transmission system of the whole S-band satellite communication system are studied,it proposed to be constructed a new type of satellite emergency communication system with low rate of information transmission,the system must use spread spectrum technology of spreading gain higher(about 40 d B or so),the use of miniature terminals and antennas at the same time should support mobile communications to provide a higher flexibility,and the maximum capacity of the system is given.Thirdly,researched on the algorithm of speech coding compression,and the voice communication process of based on code rates of 600 bps is designed,at the same time,the synchronization technology of the system has been studied,using the intrinsic relationship between carrier loop coherent integration time and information rate of the data transmission has to achieve bit synchronization,by concentrating insert eight fixed synchronous code,the received data is transferred to the right group,at the same time,the 180 degree reversed-phase of the data bits are identified and the frame synchronization is completed,the scheme of the hardware implementation which the modulated baseband based on FPGA of S-band satellite emergency communication system with low rate of information and the demodulation base band on the navigation chip was designed,the schematic diagram of system composition,the internal module and the working process are given,the chip selection and realization function of each module are discussed,the scheme of hardware implementation of multi-user receiving equipment is designed,the distribution of the user spreading code is given.Finally,the experimental situation of S-band satellite emergency communication system with low rate of information is introduced,measured data are presented in the Chinastar-6A transponder under different working modes,it shows the feasibility and validity of the whole communication system,the applications of communication system modulation module in the indoor scene for emergency communications to provide location services is analyzed,and the specific format of message and the test results are given.