An efficient constant-Q spectrum analyzer architecture using polyphase filter bank

In this paper we present an extremely efficient constant-Q spectrum analyzer. By using half-band filtering and 2-to-1 down-sampling, the traditional analyzer successively shifts lower octaves to the same spectral interval so that the same post-processing can be applied to all of them. To decrease the total workload of such a structure a 4-path polyphase filter could be used to perform a 4-to-1 down-sampling before processing the octaves in the proportional bandwidth filter bank; this engine down-samples the current octave simultaneously translating it from quarter sample rate to base-band. In this paper we do much better! We propose a spectrum analyzer that uses only a 4-path polyphase channelizer along with a proportional bandwidth filter bank. The 4-path polyphase channelizer is used to perform 4-to-2 down-sampling. It is able to simultaneously shift lower octaves to the same spectral interval and translate the current octave to base-band allowing the proportional filter bank to work on a reduced sampling rate and decreasing the total workload of the system. To further reduce the workload recursive filters are used to implement the proportional bandwidth filters. A workload analysis along with a comparison between traditional and proposed constant-Q spectrum analyzer is also shown in this paper.