why always interpolation then decimation???

Discussion in 'Homework Help' started by rsashwinkumar, Nov 1, 2011.

  1. rsashwinkumar

    Thread Starter New Member

    Feb 15, 2011
    Why generally while combining both interpolation and decimation,
    we perform interpolation first followed by decimation???
  2. steveb

    Senior Member

    Jul 3, 2008
    Decimation reduces the information content and signal bandwidth. If you interpolate after decimation, you will be less accurate than if you do it before decimation. Presumably, the purpose of interpolation would be to get the approximate data point values at times that you don't have that data so that, when you decimate, you have the necessary datapoints needed in the decimated signal. Interpolation of the undecimated data might provide very good estimates of those values. If you do the reverse, you will have erased key information content needed to provide the most accurate estimation of the required data point values.