Simulink IIR filter coverification - Incomprehensible work

I created in Simulink IIR filter (direct form II transposed). Made the same behavioral model in Hdl. Calculated coefficients for a single band parametric equalizer audio (Gain, Fc, Q). I apply noise to both models. Model on Hdl work in double. I compare the results of the Hdl model and the Simulink model, аmplitude frequency response are the same, except for the reference level, in Simulink it is 0 db, like the test noise, and in the Hdl model it is offset by about minus 20 db. What could be the reason, what I do not understand?

Answer 1

[Kiran Kintali]

I understand you are using double precision floating point model and trying to generate HDL from the Simulink model using HDLCoder and having some issues. Am I correct and can you share your model for further debugging?

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[sergey plyukh]

Hi Kiran!

Thanks for the response. Sorry for the late reply. I myself solved my problem.

But there is one question. Why when comparing the frequency response of a Parametric Equalizer Filter and a test filter (coefficients are calculated according to the Cookbook formulae for audio equalizer biquad filter coefficients Robert Bristow-Johnson), the frequency response is different - they have different Q factors with the same settings?

Best regards,

Sergey.