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Uniform Modulated Filterbank

Module by: Phil Schniter

A modulated filterbank is composed of analysis branches which:
  1. Modulate the input to center the desired sub-band at DC
  2. Lowpass filter the modulated signal to isolate the desired sub-band
  3. Downsample the lowpass signal
The synthesis branches interpolate the sub-band signals by upsampling and lowpass filtering, then modulate each sub-band back to its original spectral location (see Figure 1).
uni_f1.png
Figure 1
In MM-branch critically-sampled uniformly-modulated filterbanks, the kkth branch has a modulation frequency of ± ω k =2πMkradians ± ω k 2 M k radians , a lowpass cutoff frequency of πM M radians, and a downsampling/upsampling factor of MM.
The most common way to implement this type of uniform modulated filterbank is through the use of polyphase filterbanks and DFTs.

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