| How to implement the transmission of data of the flight parameters and audio signal simultaneously through airborne analog radio transceiver is researched in this paper. The principle is: at the transmission part, firstly the digitized and compressed speech signal and the data are multiplexed. Secondly, the data stream is encrypted, convolution-encoded and interleaved. Thirdly it is differentially encoded and digitally π/4-DQPSK modulated. At last it is through the D/A converter and transmitted to the airborne analog radio. At the receive part, the received signal firstly is filtered, amplified, amplitude-limited and goes through a A/D converter, then the data stream is π/4-DQPSK demodulated, differentially decoded, deinterleaved and Viterbi decoded. Finally the signal is decrypted, demultiplexed and restored to the original speech signal and original data. This system is based on the Software Radio conception and whole-digital receiver principle and use DSP chips as its operating platform. It implements the baseband signal processing and modulation/demodulation through software. The research shows the above scheme has the feasibility. This paper analyzes the operating principles of this system in details and focuses on my work which includes the system's software designing, debugging and simulating.
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