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FIR High-pass filter bad attenuation

Question asked by MartinKristensen on Oct 25, 2010
Latest reply on Nov 29, 2010 by gpan

Hi all

 

I am working with EZ-Kit lite 21369.

 

I have made a FIR lowpass and highpass blackman filter. This has a attenuation at 74 dB in the stopband.

My lowpass filter is okay, but the highpass filter do not have this attenuation, and its impulsresponse is very noisy, see picture, its a blackman filter with 97 coef.

 

I get the same problem if i'm designing a Equiripple with a attenuation of 100 dB in the stopband, there the attenuation in the high pass filter is 50-60 dB.

 

What am I missing?

 

The AD1835 is set to a samplerate of 48kHz

 

I hope somone can help, thanks

 

 

Martin Kristensen

Denmark

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