| A communication system based on spread spectrum technology for the transmission of multiplexed testing signals is provided in this paper. There being kinds of noise in the environment of measuring and controlling, the signals are extremely easy to be disturbed during the process of transmission. When multiplexed testing signals being transmitted, conditions will be worse. Spread spectrum has the advantage of being resistant to interference as well as being reliable. At the same time, using the orthogonal or approximately orthogonal characteristic of spreading sequence, multiplexed testing signals can be transmitted at the same time and the same frequency band.The improvement of the paper lies in: Testing signals are multiplexed directly after the spectrum of each signal alone being spreaded by its spreading sequence, which makes the system be simplified, enhances its anti-jamming allowance and improves the signal transmission reliability.Four major parts are included in the paper. Firstly, three methods of signal duplicate and the basic concept of spread spectrum communication technology are given in this paper. Secondly, common spreading sequences are described, their characteristics are also compared and simulated, and Gold sequence which cycle is 127 is used in this system. Thirdly, the merits and shortcomings of methods for the spreading sequence synchronization are presented, and the skidded correlation testing method is selected to realize the receiver synchronization and simulated using MATLAB/Simulink. Finally, the overall design of multiplexed testing signals based on DS spread spectrum technology is carried out and simulated according to the performance index of this system, which considers the being of kinds of noise, takes corresponding measures and can be applicable to the transmission of the analog signals and the digital. The simulation result conforms to the design requirement. |
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