The Filtered Spectral Rotation Measure

Many signal processing techniques were proposed in the past to identify the so-called period-3 component in the protein coding regions of DNA sequences. Most of these methods evaluate the magnitude of the output of an M-point sliding window DFT at the frequency k = M/3. In this paper, we introduce a new multirate DSP approach that computes the phase of the output of the sliding window DFT at the above frequency. We first show that, similar to the magnitude case, the phase component is completely denned by the so-called filtered polyphase sequences. We then propose the filtered spectral rotation measure for detecting the periodicity in genetic regions by modifying the polyphase sequences using digital filters. Experimental results show that the new filtered measure performs better than the existing non-filtered approaches.