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Drawbacks of Classical Filterbank Designs

Module by: Phil Schniter

Summary: Modules provides a very brief description of the drawbacks to the classical filterbank designs and introduces the need for more modern approaches.

To begin with, the reference to "classical" filterbank designs, generally refers to the filterbank types that you should have seen up to now. These include the following types, that can be reviewed if necessary:

Drawbacks to Classical Implementation

The classical filterbanks that we have considered so far (those listed above) give perfect reconstruction performance only when the analysis and synthesis filters are ideal. With non-ideal (i.e., implementable) filters, aliasing will result from the downsampling/upsampling operation and corrupt the output signal. Since aliasing distortion is inherently non-linear, it may be very undesirable in certain applications. Thus, long analysis/synthesis filters might be required to force aliasing distortion down to tolerable levels. The cost of long filters is somewhat offset by the efficient polyphase implementation, though.

That said, clever fliter designs have been proposed which prevent aliasing in neighboring sub-bands. These designs include the following references: Rothweiler, Crochiere and Rabiner, and Vaidyanathan. As neighboring-subband aliasing typically constitutes the bulk of aliasing distortion, these designs give significant performance gains. In fact, such filter designs are used in MPEG high-performance audio compression standards.

References

  1. J.H. Rothweiler. (1983). Polyphase quadrature filters - A new subband coding technique.
  2. R.E Crochiere and L.R. Rabiner. (1983). Multirate Digital Signal Processing.
  3. P.P. Vaidyanathan. (1993). Multirate Systems and Filter Banks.

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