Discussion in 'Homework Help' started by joeDiHare, Aug 13, 2010.

  1. joeDiHare

    Thread Starter New Member

    Aug 13, 2010
    I was asked to design a BANDPASS filter by this istruction (in Matlab):
    "2-stage 4th order filter with Q=4 and 12dB/octave high-pass and low-pass rolloffs".
    But I don't really understand what I am asked. Is this band pass made of a 4th order high pass followed by a 4th order low pass, and Q is the quality factor which defines the width of the band (how distant the two cut frequencies are) ??
    And still, I would not know how to implement the 12dB rolloff in Matlab.
    Thanks for your help.
  2. Ghar

    Active Member

    Mar 8, 2010
    Sounds like 4th order refers to the entire filter, so that would be a 2nd order low pass cascaded with a 2nd order high pass.

    A first order filter gives a 6dB/octave roll off while a 2nd order filter gives 12dB/octave roll off.