说明：  推荐锁相环的两本书。一本是Floyd M.Garder著，姚建清译的《锁相环技术-第三版》； 另一本是台湾国立中兴大学的PLL及应用。
(Two books on PLL are recommended. One is the third edition of PLL technology by Floyd M. garder and translated by Yao Jianqing; The other is PLL and application of National Chung Hsing University in Taiwan.)