摘要
常规DDS频率合成方案无法合成超过1/2采样频率的信号频率,这给DDS器件的应用带来了很大限制。在实际应用中通过对DDS器件的输出信号频谱进行分析发现,其频谱中除包含设计频率以外还包含特高频(UHF)频段的镜像频率分量。计算发现这种镜像频率与合成的设计频率成线性关系,故可通过计算确定镜像频率并通过选频滤波提取它们从而获得UHF信号。为扩展DDS器件的应用范围,提出了利用镜像频率实现UHF频率合成方案,设计了基于AD9912芯片的频率合成系统,编写了相应的控制程序。最终实现了利用DDS器件合成了1 500 MHz信号的预想。
Conventional DDS can＇t synthesize a frequency beyond the 1/2 frequency of sampling clock, which restricts the applications of the DDS device. In the analysis of DDS output signal in practical application, besides the design frequency, there are still some image frequencies belong to UHF band, And there is a good linear relationship between this two kinds of frequencies. So it provides a way to calculate the image frequencies and get them by filtering. To expand the applications of the DDS device, this paper proposes a method of UHF frequency synthesis which makes use of image frequency. A frequency synthesis system was designed and the corresponding control codes were programmed as well. Achieved the requirement of synthesizing a 1 500 MHz UHF signal by DDS device.
出处
《电子设计工程》
2012年第22期175-178,共4页
Electronic Design Engineering
