对锁相环型频率综合器中的高速分频器进行了较为深入的分析。比较了同步分频器和异步分频器，表明了异步分频器在高频应用中的特点。对相位切换型异步分频器中第1级和第2级2分频电路的实现方案进行了仔细分析和对比，并针对Wang提出的2分频电路中存在的电荷分享问题提出了改进方案，仿真显示改进后的电路有效解决了电路中的电荷分享问题。采用Chartered 0.35μm 2P4M CMOS工艺，对第1级与改进后的第2级2分频电路整体仿真显示，电路的最高工作频率为3.3GHz，电流消耗为1.9mA。

In this paper, the design of the high-speed divider in the PLL frequency synthesizer is investigated. The characteristics of circuits concerning speed and power are compared between the synchronous divider and the asynchronous divider. Considering the different demands for the divide-by-2 circuits in the phase-switching asynchronous divider, several different circuits topology of the divide-by-2 circuits are presented. And the charge sharing problem of the divide-by-2 circuit in a reference paper is solved in this paper. According to the simulation results, the highest working frequency of the first and the improved second divider-by-2 circuits is 3.3GHz, and the current consumption is 1.9mA.