在模拟信号的数字化处理过程中,模拟信号首先通过模数转换器(A/D)转化为数字信号,在数字设备上完成处理后,再通过数模转换器(D/A)还原为模拟信号。从时域看,信号形态经历了模拟信号到数字信号再到模拟信号的过程;从频域看,则是从模拟频谱到数字频谱再回到模拟频谱的过程。因此,研究模拟频率和数字频率之间的对应关系,对于深入理解数字信号处理及傅里叶变换之间的关系有促进作用。 In the process of digitizing analog signals, analog signals are first converted to digital signals by analog-to-digital converters (A / Ds), processed on digital devices, and then reduced to analog signals by digital to analog converters . From the time domain, the signal morphology goes through analog signals to digital signals and then to analog signals. From the frequency domain, it is the process from analog spectrum to digital spectrum and back to analog spectrum. Therefore, studying the correspondence between analog frequency and digital frequency can promote the understanding of the relationship between digital signal processing and Fourier transform.