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Multirate Signal Processing

Abstract

In single-rate systems, only one sampling rate is used throughout a digital signal processing system, whereas in multirate systems the sampling rate is changed at least once. This laboratory deals with the realization and analysis of multirate systems. In the first experiment we will examine the effects of decimation and interpolation. Next, a tree structure filter bank with quadrature mirror filters (QMFs) will be built and the quality of the reconstructed output signal will be discussed. Finally, we will analyze an example where the short-time Fourier transform (STFT) is used as a filter bank.

Key takeaways

  • The output signal is at a lower sampling rate, and thus has a lower bandwidth (f s /2) than the input signal (f s /2).
  • The resulting signal has a sampling rate f s = Lf s , and a spectrum that includes periodic images of the original signals spectrum.
  • After m stages, a filter bank with 2 m outputs is built and the output signals are decimated by a factor of 2 m with respect to the input signal.
  • In each stage of the synthesis filter bank the sampling rate of the signals has to be increased again.
  • For H = 1 the bandpass output signals have the same sampling rate as the input signal.