摘要
详细分析了直接数字合成(DDS)和锁相环(PLL)的基本原理、特点及相位噪声特性。将DDS与PLL技术结合,取长补短,可以在不降低杂散性能要求的前提下实现小步进的频率合成器。在此基础上提出了一种DDS+PLL+混频的L波段小步进频率合成器的实现方案。根据方案,选择DDS芯片AD9850和PLL芯片ADF4112来搭建电路。给出了试验测试结果。测试结果表明,在L波段实现了相位噪声-94dBc/Hz@1kHz,杂散抑制-60dBc,频率步进1kHz,验证了该方案的可行性。
Firstly the basic theory of DDS and PLL, as well as their characteristics and phase noise properties, has been analyzed in detail. Combining the DDS and PLL technology is a method to achieve fine step size without degradation of spurious characteristics. The integrative frequency synthesis technology of DDS ＋ PLL ＋ Mixer is adopted in the final scheme. According to the request of the scheme, DDS chip AD9850 and the PLL chip ADF4112 have been chosen to establish the system circuit. Finally, experimental results are introduced. Its specifications show as following： output frequency at L -band, phase noise - 94dBc/Hz @ lkHz, spurious - 60dBc, step size lkHz. So the feasibility has been verified.
出处
《无线电工程》
2007年第6期60-61,64,共3页
Radio Engineering
