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how the Q of a filter in SigmaStudio works?

Question asked by dimitris. on Nov 15, 2016
Latest reply on Nov 27, 2016 by matthijs

Hi forum,

 

In SigmaStudio I am using a second order general parametric EQ filter. 

I am setting a f0 = 500 Hz, a dBboost of -12 and a Q of 5. 

I then plug in the probe and the stimulus on the filter and check the frequency response. 

The result does not match my Matlab implementation of the filter. I also compare the frequency response of the filter with the same coming from another DSP tool and it also does not match the curve I see in SigmaStudio. But it does match my matlab implementation.

 

I know SigmaStudio is probably defining the Q differently than other tools, according to this:

General Filters [Analog Devices Wiki] 

 

However, none of the the Q = 5 or the Q' = 5 seem to give me what the other tools give me for a Q = 5.

I can more or less match the response of the filter in SigmaStudio if I set the Q = 2.5 and Q' = 1.25.

Why is this and how can I match the Q in a SigmaStudio filter to those that other tools give me?

 

thanks

Dimitris

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