USB TT&C System Transponder Based On Open Source SDR

With rapid development of aerospace.Our country sees great need for space exploration,with which is the urgent need for more and more TT&C tasks within one single satellite.Some of the satellites simply carried on more transponders,each transponder for a specific TT&C task,for example the Zhuhai I satellites had three transponders each,for the satellites have the need for S-band,UV-band and X-band TT&C tasks,which turned out to make the satellites bigger and heavier.In another condition when there is a new task for the satellites,in the traditional way,all we can do is to send another satellite to the space.In order to solve the problems,we need a universal transponder with easier ways to update for new tasks.This paper begins with the background and the applications of the transponder,after witch is a brief introduction of the TT&C ranging unit and velocity measurement.Based on the introduction,the paper describes the way to implement the transponder,and the software part is what really matters.The transponder is based on USRP,which contains a Zynq706 board and a fmcomms2 board.The fmcomms2 board carries a AD9361 chip,which is a universal transceiver with wide bandwidth.The zynq706 board contains a ARM processor and a FPGA.The software part can be divided into two parts: the PS(Processing System)part and the PL(Processing Logic)part.For the PS part,we used the open source software kit GNU Radio which is a Linux based SDK,who has abundant DSP modules,which can help saving time to finish the transponder's design.As for the PL part,we used the FPGA to help the ARM core with digital signal possessing.This thesis end with the test of the transponder,featuring the frequency accuracy,modulation rate etc.The test result turns out well,which makes it a perfect beginning of using this platform to implement transponder with other frequency.