【摘要】 与整数分频电荷泵锁相环不同,小数分频电荷泵锁相环中电荷泵对锁相环的性能有更大的影响,电荷泵的各种非理想因素将降低PLL输出相位噪声和杂散的性能.重点分析了电荷泵两种非理想因素对小数分频锁相环相位噪声和杂散的影响:非线性和电流失调.此外还分析了电荷泵电流源噪声对小数分频锁相环的影响,分析结果为优化电荷泵的电路设计提供理论依据.更多还原

【Abstract】 Different from integral charge pump PLL,the charge-pump(CP)within Fractional-N PLL imposes more influence to the performance of the circuit.The non-ideal factors of CP will decrease the phase noise and spur of fractional-N PLL.This paper analyzes the effect that two kinds of non-ideal phenomena of CP put to the phase noise and spur of Fractional-N PLL:nonlinearity and current-mismatch.What is more,how the noise of CP current source is harmful to phase noise of fractional-N PLL is depicted.The conclusions provide theory supports for the optimization for the designing of CP circuits.更多还原