基于DDS的直接数字调频信号频谱解析式

Analytical Expression of Frequency Spectrum of Direct Digital Frequency Modulated Signal Based DDS

基于DDS的直接数字调频(DDFM)信号频谱不同于标准FM信号,得到了正弦调制DDFM信号的频谱解析式,解析式和文献测量结果吻合良好。推导方法可用于推导其他类型DDFM信号(如线性调频DDFM信号)的频谱解析式,并有助于深入研究DDFM信号的频域指标。同时,仿真研究了ADC与DDS幅度量化效应对DDFM信号频谱杂散的影响,得出了量化杂散影响因素的准定量关系。

Frequency spectrums of direct digital frequency modulated （DDFM） signal is different from that of standard FM signal. The analytical expression of spectrum of sinusoidal modulation DDFM signal was obtained firstly. The analytical expression fit the measurement by former literature well. The derivation method could also be used for obtaining spectrum expression of other DDFM signal （ such as LFM DDFM signal）, and is useful for deeply study of frequency domain measurement of DDFM signal. And also, the effects of ADC and the DDS amplitude quantization on the power level of the spurious spectrum are studied through computer simulation, and the quasiquantitative relationship between spurs level and it＇s determining factor is obtained.