用微机实时地对大地电磁测量数据进行傅氏变换,求算功率谱,这种方法称为级联分样技术(以下用CD表示)。它对32点时域数据进行正弦,余弦变换。每一次分样前都先对数据进行一次低通滤波,然后每两点中丢掉一个数据作为下一级傅氏变换数据。求出的谱值在对数域上成等间距分布。文章阐述了级联分样的理论和在微机上实现的方法,并把此方法与快速傅氏变换法作了对比。 Real-time computer using the microcomputer for the electromagnetic measurement of the earth Fourier transform, calculate the power spectrum, this method is called cascaded sub-sampling technology (hereinafter referred to as CD). It performs a sine and cosine transform on 32-point time-domain data. Before each sub-sample data are first a low-pass filter, and then lost every two points as a next-level Fourier transform data. The calculated spectral values ​​are equally spaced on the logarithmic domain. The article expounds the theory of cascaded decimation and the method implemented on the microcomputer, and compares this method with the fast Fourier transform method.