The principal of the digital communication theory and the relational theory of the synchronization are introduced in fourth chapter . in fifth chapter , author detailedly describes the methods of two kind digital phase - locked loop , expounds the processing of design and implementation by fpga 第四章介紹了數字通信中位同步的相關理論,并在第五章詳細敘述了兩種數字鎖相位同步的原理,并論述了使用fpga設計實現這兩種位同步方法的過程。