Try to fill the Table of an FIR Filter (1701)

Hi Stefan,

I used a basic FIR filter coefficient generator here to create an example:

http://www-users.cs.york.ac.uk/~fisher/mkfilter/hilbert.html

I took the coefficients and copied them into SigmaStudio. I then clicked the probe button, then the stimulus button, and was able to view the frequency response.

https://ez.analog.com/cfs-file/__key/communityserver-discussions-components-files/396/539edc53f703361ca55f38d0affe223a.bin

The SigmaStudio project file is attached. Please use it as a guide.

Hello, I have a similar question about FIR Filterdesign. I am just getting started so please don't blame me, if my qestion is dumb :

Why does SigmaStudio accept values for FIR coefficients higher than 1? Is this a Bug or is there a possibility that values of FIR coefficients could be higher than 1 or less than -1?

I'm just trying to understand what the Software exactly does and how to interpret the results.

A short Answer would be great!

regards

Alex

The filter coefficient parameters are in 5.23 format, which means that the values can be in the range of +15.999... to -16. SigmaStudio does not limit the filter coefficients beyond this numerical format. With coefficients set >1.0, the output of the filter will be at a greater level than the input. The SigmaDSP's internal numeric format is the same 5.23 as the parameters. This number format on the data allows for gains of up to +15.999..., or +24 dB internally before the data will clip. Of course, this data must be limited to 1.23 (+/-1.0) on the outputs, but internally this extra headroom preserves dynamic range in the signal processing.

Hi, maxidcx.

I'm using chip ADAU 1701, fs=48000.

Sorry, I am a newbie in filter designing.

I would like to design an IIR Notch filter at 1kHz. I used "Fixed-Point Table Generator" to get the coefficients.

Then, I feed that IIR output into another FIR filter to correct the phase shift. I'm using 'rephase' to design the FIR filter and get 128 taps of impulse response and then fill in the FIR filter in SigmaStudio.

Below is capture screen scope IIR:

IIR filter generates some phase shift around 1kHz. (Q=1, Butterworth, cutoff at 1kHz, fs_1=850, fs_2=1150).

But I could not get the expected result in Simulation Probe. I guess the output should be a linear line 0 degree.

This is the screen of phase display:

Am I using wrong method to get the FIR coeff? Or the phase display is incorrect?

Hope to hear from you soon.

Thanks alot,

JCB

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