简述了宽带小步进频率合成器的常规实现方法。着重介绍了一种基于DDS＋PLL结构简洁的宽带小步进频率合成器。DDS在锁相环中用作小数分频器，对合成器的相噪指标进行了深入的分析，并详细阐述了合成器的设计思想和电路实现方法。结合要求给出合成器电路板的合理布局，同时完成了样机设计。测试结果显示，合成器具有大带宽、小步进、低相噪等特点，可应用于小型化的雷达信号模拟器。

A few of methods for designing broadband synthesizer with small step are described in brief.A kind of broadband and small frequency-step synthesizer based on direst digital synthesis(DDS) and phase-locked loop(PLL) is emphasized in the scheme.DDS was used as decimal frequency divider.Phase noise,design principle and circuits realization of synthesizer are analyzed in more details.The reasonable layout of printed circuit board(PCB) is presented.The testing results show that the bandwidth of synthesizer is broad,frequency-step is small and phase noise is low.It can be used in radar signal simulator in minizature.

TN741