Designing For Digital Phone System Based On The Laser Communication

The space laser communication is one way of communication that is widely used in the military realm currently. As a carrier wave of communication, laser has a lager band of frequency to make use of, and can raise the communication capacity by several decuples by adopting wavelength division multiplex technique. Besides, It has a better capability to keep secrecy. And telephone is one of the speech systems most commonly used. This paper, targeted on the characteristics of speech signal based on laser communication, tries to develop a kind of digital phone system to process the terminal speech signal.Firstly, laser communication of speech signal is realized by the electro-optic modulator. After the signals are received, they are processed with the digital phone hardware platform. This platform, with TMS320C54CST processor as the core, mainly includes laser signal acquisition and transformer module, speech signal processing module, program saving module, D/A audio output and LCD module.Secondly, on the basis of designing digital phone hardware system, the paper has designed the system's software structure, giving the whole process of designing the system's software. It emphasizes on the way of speech signal algorithm, especially the design method of FIR filters. It studies the design method of two kinds of FIR filters based on MATLAB. On the basis of imitation, the paper designs the system initialization program and FIR filter program by using DSPC54x assembly language. It also designs the RTDX program based on MATLAB and gives the detailed process of designing the Boot Loader program. At last, based on the hardware target board, the paper realizes the synchronous imitation and debugging of digital phone by compiling CCS Project document.This digital phone system can directly receive the speech signal which is transmitted by the laser communication and make analysis as well as processing on it. Besides it is characterized by good capability of reducing noise and keeping secrecy. In addition, it provides interface for the expansion of other functions. As long as we make some changes on the software of the telephone system, it can be used on so many special occasions as strong-noise industrial scene and secrecy-keeping safe telephone with the need of keeping military secrecy.