Research On Application Of Spread Spectrum Communication In The Civil Air Defense Alarm System

Modern wars are high-tech wars,efficient and reliable air defense alarm directly relate to national interests and people's lives and property security.As the electromagnetic environment worsening,the performance requirements of civil air defense warning system is getting higher and higher.we need to upgrade the existing civil air defense alarm communication system.The development of electronic and communication technology has provide an opportunity for the update of the civil air defense alarm system.Due to the characteristics of spread spectrum communication technology,such as strong anti-interference and code division multiple access and low intercepted rate and strong security,these characteristics have been widely used in GPS and wireless sensor networks.If we can put the spread spectrum technology into the civil air defense alarm system,it will greatly improve the communication quality of the existing system.This paper analysis the characteristics of civil air defense alarm system and the development of civil air defense alarm system at home and abroad.this paper expounds the basic principle and characteristic of the direct sequence spread spectrum system,and puts forward a communication solution of civil air defense alarm system what based on direct sequence spread spectrum.We use the advantage of the parallel architecture of FPGA in digital signal processing,and choose FPGA as a means of realization what has good scalability.This paper rely on spread spectrum communication and software radio and related theory,we compare and analysis the implementation methods of the choice of pn code and carrier synchronization and pn code acquisition,then determine the concrete implementation plan of the system.We design the related function son module by using Verilog HDL in Quartus ? environment.The system is divided into launch side and receive side.The launch side include the String and conversion,difference coding,level 6 of m sequence generator,forming filter,NCO and digital frequency conversion above.the receive side include the digital frequency conversion below,digital loop filter,digital matching filter and so on.we use EP1C12Q240C8N as the core and design parts of hardware circuit,including D/A conversion chip circuit,switching power circuit,clocking circuit,Flash and SRAM circuit and the serial interface by JTAG configuration of EPCS4 device configuration circuit and so on.The idea of this paper has great theoretical and use value in the civil air defense alarm system based on the spread spectrum communication.