直接数字式频率合成器的杂波抑制度分析

Interference Wave Restraint Analysis of the Direct Digital Frequency Synthesizer

着重研究了直接数字式频率合成器(DDS)的频谱特性。以信号的数学模型和频谱为出发点,归纳出DDS在有相位截断时信号的杂波抑制度的计算,并得到杂波抑制度与频率控制字、截断误差、D/A位数的关系,为研制低杂散DDS提供一定的理论依据。

The spectrumcharacteristic of the direct digital frequency synthesize r(DDS )is mainly stud-ied in this paper.On the basis of math ematic model and spectrum analysis,the calculation formula of inter-ference wave restraint is deduced,meanwhile the phase error sequence of DDS is introduced,finally the rela-tion among the frequency controllin g word,the spurious level phase accu mulation byte,interrupting error byte and D /A byte is obtained,which s erves as theoretical basis for studying the low spurious DDS.