Basing on the discussion of principle and characteristic of direct digital frequency synthesis(DDS) and phase-locked loop frequency synthesis(PLL),a design scheme of frequency synthesizer combining direct digital synthesis used for modern radio is given.

• 介绍了DDS(直接数字频率合成)技术及PLL(锁相环)频率合成技术的工作原理及特点,给出了现代电台设计中基于DDS的频率合成器的设计方案。