说明：  在谱分析中，数据长度N，采样频率fs，频谱中的分辨率为df=fs/N。为了提高谱分析中的分辨率，常用ZOOMFFT，这里给出了相应的MATLAB程序。
(In spectrum analysis, the data length N, the sampling frequency fs, the spectrum of a resolution of df = fs/N. Spectral analysis in order to improve the resolution, commonly used ZOOMFFT, here the corresponding MATLAB procedures.)