| Civil air defense alarming system(CADA) plays a significant part in city security. Although, communication mode by fixed frequency is widely adopted in domestic CADA resulting in being jammed by tactical EMI and being disabled in battlefield and more easily being intercepted and being controlled with no authorization, with poor anti-jamming, reliability and encryption. It is better to introduce hopping frequency transceiver to CADA, which can anti-jam efficiently and improve encryption making use of the features of hopping frequency.The research of this task concentrates on the design and implementation of the synchronization mechanics in hopping frequency transceiver served for CADA on the basis of project "Qingdao civil air defense alarming system".The theory of hopping frequency is researched in the task, analyzing its 3 key technologies containing frequency synthesizer, pseudo-random sequences and synchronization deeply. A strong emphasis has been laid on the research of varieties of meanings of capturing and tracking and their comparison.And then, a complete scheme about the synchronization mechanics is put forward, including network architecture,optimization of the synchronization information, initial establishment of the network, late joining and synchronization holding. Furthermore, aiming at the peculiar characters of the CADA, one-to-more hopping,relaying hopping, asynchronous network establishment and self-adapting hopping are brought forward.Lastly, in view of the quantity of the data and cost etc., the implementation scheme of "MCU+CC1100" is put forward, with RF circuit constructed, the interface with the micro-controller, procedure of power-on and configuration method designed. Emphasis has been laid on the controlling DFA, frequency hopping,frequency calibrating, channel quality sense and output power programming, in order that the synchronization mechanics can running efficiently. |
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