Design And Implementation Of The Radio Station Based On Direct Sequence Spread Spectrum

In face of the increasing serious traffic problems in the cities, rail transit with efficient, safe, rapid features has developed rapidly. As the development and integration of computer technology, communication technology and control technology, the CBTC system (Communication Based Train Control)has been widely applied.The research of safe and reliable train-ground communication is the basic issue of the CBTC system.By analysing and researching the typcial CBTC train-ground communication technology,a spread spectrum wireless communication based train-ground communication system solution is put forward and a direct sequence spread spectrum radio station is implemented in this thesis.The technology scheme,the performance indicators and requirements of the software and hardware are presented in details.To begin with, a deep research in spread spectrum communication technology which includes its theoretical basis,mathematical model and physical model is done. After compared the advantages and disadvantages of frequency hopping spread spectrum system and direct sequence spread spectrum system, the later is selected to be the spread spectrum approach of the radio station.On the hardware work, the circuit schematic and printed circuit board layout design of the radio station which uses ATmegal28L as its control unit and CYRF6936 spread spectrum communication SOC as its RF core is completed in the Altium Designer. The electromagnetic compatibility of the printed circuit board, radio frequency circuit layout, microstrip transmission line, RF front-end circuit is also designed and analysed in the hardware design section. On the software work, the SPI driver and application programs of CYRF6936, serial communication protocols and wireless communication protocol programs are completed in the ICCAVR.In addition, the system management and analysis software is developed in the VC++6.0.At last, the feasibility of the spread spectrum wireless communication based train-ground communication system solution is verified by the system tests.The implementation of the radio station and the problems which solved through the design and test process have an important reference value on the application of spread spectrum communication technology in urban rail transit.