Why are only the filter coefficients of the first section of a filter returned when I try to export all the filter coefficients in FDATool in Filter Design Toolbox 2.5 (R13SP1)?

Question

MathWorks Support Team 2009-6-27

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https://ww2.mathworks.cn/matlabcentral/answers/96954-why-are-only-the-filter-coefficients-of-the-first-section-of-a-filter-returned-when-i-try-to-export

I designed an IIR Elliptic Bandpass filter using FDATool. The filter has a Direct Form II, second-order-sections structure.

I then turned the quantization on.

Finally I go to "File->Export" to export the filter coefficients to a text file. In the text file, I only see the filter coefficients of the first section.

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Answer 1

MathWorks Support Team 2009-6-27

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/96954-why-are-only-the-filter-coefficients-of-the-first-section-of-a-filter-returned-when-i-try-to-export#answer_106304

This is a bug in Filter Design Toolbox 2.5 (R13SP1) in the way that FDATool handles exporting filter coefficients. It was fixed in Filter Design Toolbox 3.0 (R14).

To work around this issue in Filter Design Toolbox 2.5 (R13SP1) and before, convert the filter structure to Single Section before exporting filter coefficients.