摘要
由于DAC的非理想特性,DDS信号频谱解析式在较高频输出时与实测差别较大,本文旨在求出更符合实际的DDS信号频谱解析式。定义了"较高频DDS输出"的定量概念,分析了较高频DDS输出时DAC非理想特性,特别是DAC建立时间特性,给出了由建立时间估算转换时间的近似公式,将转换时间区间的输出简化为梯形波形模型,求得相应的Fourier变换,从而得到新的频谱解析式。实验采用ADI公司的DDS芯片AD9851,测量了信号幅频特性,证明了较以往解析式,新解析式和实测更加吻合。
For non-ideal characteristics of DAC, there is large difference between expression of DDS＇s spectrum and measurement when output frequency is higher. The objective of this paper is to get an expression of DDS＇s spectrum fitting measurement better. In this paper, the quantitative conception of ＂higher frequency DDS signal＂ is defined; the Non-ideal characteristics of DAC is analyzed, especially the performance of DAC＇s setting time; the correlation of slew time and setting time is proposed; a simplified trapeziform model is established, then, it＇s Fourier transform is obtained; and finally,a novel analytical expression of ＂higher frequency DDS signal＂ is obtained. The experiment adapts DDS IC AD9851 produced by ADI Inc to measure amplitude spectrum of DDS signal, and the results demonstrate that comparing with former expression, the novel expression fits measurement result better.
出处
《电子测量技术》
2007年第6期46-48,共3页
Electronic Measurement Technology
关键词
DDS
频谱
解析式
数模转换器
建立时间
DDS
frequency spectrum
analytical expression
DAC
setting time
