Digital Filter Structure conversion

[HectorBilly]

I've designed a Chebyshev 8th order digital IIR filter. Labview gives the coefficients for a four second order section cascaded structure (8th order in total).

How do I obtain the equivalent direct form coefficients using LabView ?

I've tried the convert structure icon but I get the 8th order/2nd order mismatch error.

Any help appreciated.

[altenbach]

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@HectorBilly wrote:

I've designed a Chebyshev 8th order digital IIR filter. Labview gives the coefficients for a four second order section cascaded structure (8th order in total).

How do I obtain the equivalent direct form coefficients using LabView ?

I've tried the convert structure icon but I get the 8th order/2nd order mismatch error.

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Your post is very hard to understand:

• Assuming you created a subVI with your own designed filter code from scratch, you can create any outputs you want. Can you explain what you did?
• LabVIEW is a full featured programming language, and you can implement any algorithm.
• What is a "structure icon" and what exactly did you "convert" from what into what?
• Where exactly does that error occur?
• Are you using any toolkits?
• Are you using express VIs?
• What is the data (array? waveform? dynamic?, etc.)
• so! many! questions!

I recommend to attach a simplified version of your VI so we can actually understand what this is all about.

(Make sure to "save for previous", 2020 or below before attaching)

[HectorBilly]

Hi

I'm using LabView to generate coefficients for a real time IIR filter I've written for the STM32F407G Discovery board.

My program requires the IIR coefficients to be "plug in" compatible with the Direct Form 2 filter structure.

Using LabView's Signal Processing\Digital Filter Design\Design\Classical filter function I've designed a Chebyshev IIR low pass filter.

I have then connected a Signal Processing\Digital Filter Design\File i/o\Save Text function to the output of the filter in order to store the filter design to an .xml file. The .xml file gives the filter coefficients for cascaded second order sections.

My question is:

Is there a LabView function which will sit between the filter output and the save text input which will convert the cascaded second order section coefficients to Direct Form 2 coefficients prior to saving the design to the .xml file ?

Thanks.

[altenbach]

Thanks for the clarifications, now things make a lot more sense. 😄

Unfortunately, I don't have the digital filter design toolkit installed, but hopefully somebody else will be able to help.