A New Tdrss User Answering Machine If Digital Receiver Design

The main tasks in this thesis focus on intermediate frequency digitized technology for TDRSS User Transponders, which is a part of the novel technology research of transponders. It needs to research and develop a kind of IF digital receiver of the TDRSS User Transponder.As a novel space-based tracking, telemetering and command system, the Tracking and Data Relay Satellite System (TDRSS) represents a new direction in the international tracking telemetering and command field. A TDRSS User Transponder is a terminal of the user satellite in this system, in which QPSK or SQPSK modulation and direct sequence spread spectrum(DS-SS) are employed in the forward/backward links. As a result, pseudorandom code acquisition and tracking, carrier recovering, error correction and decoding functions are needed in the IF digital receiver.First, the implementation project of the IF digital receiver of TDRSS User Transponder by the FPGA and DSP cooperation design method is proposed in this thesis. Then, the software simulation system for the IF digital receiver is built up, definite word-length effect is analyzed, and some useful conclusions are derived, which provides reference for the following hardware design and debug. In the end, implementation of IF digital receiver unit of TDRSS user transponder by the method of FPGA and DSP cooperation design are completed successfully, which leads to good DS-SS IF receiver design for the signal whose carrier frequency is 3MHz, pseudorandom code rate is 3Mchips/s, data rate is 10Kbps, frequency offset is no more 1KHz, and modulation mode is BPSK.