An efficient FFT based spectrum analyzer for arbitrary center frequencies and arbitrary resolutions analysis

In this paper we present an extremely efficient FFT based spectrum analyzer that performs constant-Q spectral analysis. Each stage of the proposed structure is formed of a half-band filter and a 2-to-1 down sampler. It shifts successive lower octaves to the same spectral interval; consequently, the same octave processor can be applied in all the stages. Fourier transforms are normally used for performing equally spaced, equal bandwidth spectral estimation; their main advantage is the efficiency of the FFT algorithm. In this paper, by post processing the output of the FFT block with a frequency sliding window having variable bandwidth, we are able to achieve spectral estimations at arbitrary center frequencies with arbitrary resolutions maintaining the advantages of using the FFT algorithm. To further decrease the total workload, a 4-path polyphase channelizer is used to down sample the octaves before processing them in the FFT block.