active loop meaning in English

放射性回路
热环路

Then according to the emphasis of the design , went deeply into the theory of pll frequency synthesizers widely used , described pll ’ s working principle , structure and several types in detail , and made research and analysis of pll frequency synthesizers ’ phase noise , including the effect of the active loop filter on the phase noise , and give some methods to make improvement as well , such as changing loop filter form , reducing divide number , and increase phase detector frequency , etc . then paper introduced the principle character and phase noise analysis of direct digital frequency synthesizer ( dds ) and injection phase lock circuit , which are also important circuits in the design
论文首先对几十年频率合成器的发展进行概述,而后针对本次设计的重点,对应用较为广泛的锁相频率合成理论进行了深入的探讨,详细介绍了锁相环的工作原理、组成结构和锁相类型,并对锁相频率合成器的相噪特性进行了研究分析,包括有源环路滤波器对于相噪的影响,提出了改善相位噪声的几点措施:改善环路形式、降低分频数、增大鉴相频率等。接着介绍了直接数字频率合成器( dds )和注入锁相电路的原理特点以及相噪分析,它们也是本次设计的重要电路。