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Entry  Thu Jul 26 17:39:49 2012, Den, Update, digital noise, biquad key is working df2_bqf.pngdf2_bqf_spec.pngiir_psd_notch.pngiir_time_notch.png
    Reply  Thu Jul 26 21:31:44 2012, Den, Update, digital noise, online biquad works  df2_bqf_lp.pngdf2_bqf_lp_spec.png
    Reply  Fri Jul 27 14:30:49 2012, Jamie, Update, digital noise, biquad key is working 
       Reply  Mon Jul 30 14:24:25 2012, Den, Update, digital noise, biquad key is working lnf.png
Message ID: 7042     Entry time: Thu Jul 26 21:31:44 2012     In reply to: 7041
Author: Den 
Type: Update 
Category: digital noise 
Subject: online biquad works  


   Still I do not like huge (2n+1) harmonics in the output of the biquad filter, I do not get them in the simulations. They are absent in the time series as well. So this is not a psd-estimation effect. 

 Excitation generator created these harmonics. When I applied low-pass butterworth filter, I've got the result of online filtering close to simulations. On the second graph blue is biquad filter output spectrum, red corresponds to DF2. 1 Hz sin wave was filtered with a notch filter of Q=100, depth=300 at 1 Hz.

df2_bqf_lp.png    df2_bqf_lp_spec.png

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