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Discrete fast Fourier transform (FFT) has been widely applied to signal spectral analysis and can figure out the entire bandwidth spectrum of a signal. However, the fine structure of high resolution spectrum in a narrow band- width is required in some applications. If regular FFT is still used to figure out the high resolution spectrum, it will result in addition of data and at last sharply increase of computation and storage. Therefore, FFT is inefficient and a new method must be put forward. In the paper, the principle of zoom FFT technique based on complex modula- tion, its application to development of SLF/ELF receiver and how to obtain high resolution spectrum using the new technique are introduced in detail and also the theoretical and test results are presented.
Discrete fast Fourier transform (FFT) has been widely applied to signal spectral analysis and can figure out the entire bandwidth spectrum of a signal. However, the fine structure of high resolution spectrum in a narrow band-width is required in some applications. FFT is still used to figure out the high resolution spectrum, it will result in addition of data and at last sharply increase of computation and storage. Thus, FFT is inefficient and a new method must be put forward. In the paper, the principle of zoom FFT technique based on complex modulation, its application to development of SLF / ELF receiver and how to obtain high resolution spectrum using the new technique are introduced in detail and also the theoretical and test results are presented.