A Research On Algorithm And Implement Of The DS Receiver In Dual-Mode Transponder

To realize tracking and data relaying of the user spacecraft, transponder is indispensable. The new universal transponder should have two modes to adapt to both the PM modulation mode of traditional Unified S Band telemetering and command system and the Spread Spectrum mode. The thesis does some research work for manufacturing the new type of transponder to accommodate flexibility.The thesis introduces the application of the software radio in our task and analyses the performance exaltation caused by the IF sampling in the system. In the third chapter, a new noncoherent sequential detector using in PN code acquisition under the low SNR and big frequency offset condition is studied on the base of the Wald's optimum detector. The new method can get over the performance descend in the traditional way when frequency offset, PN chip asynchronism and data modulation exist. Also the numerical comparison in computer simulation is made between these two methods. In the fourth chapter, a series of algorithm are proposed which can be used in the new transponder working in low SNR, including the PN code acquisition algorithm of parallel six routes sliding-correlation, the PN code tracking algorithm using DPLL, the carrier acquisition and tracking algorithm seasoned with high dynamic aircraft, the carrier phase recovery algorithm realized by the sin look-up table, the synchronism algorithm of very long telemeter PN code leaded by the short spread-spectrum PN code, etc. The flow chart of these algorithms and the numerical results of computer simulation is given. To implement the algorithm, the hardware is designed. All these research work will give a valuable reference to the manufacture of the new transponder.