# LabVIEW

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## FIR filter with zero phase (no phase shift)

I would like to implement an FIR filter without a phase shift. I  am thinking this might be achieved by generating forward and reverse  co-efficients from the FIR and then feed that into the zero phase filter. But ideas on how to implement this will be appreciated.

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## Re: FIR filter with zero phase (no phase shift)

Finite Impulse Response filters have --

Wow, A Finite Response -ooh. So, they will need to collect and process the input data in (well, a "Finite" manner!)

Those finite (Known) parameters may be Known!  See CA for that!

Now, can you give data inputs and desired outputs?

"Should be" isn't "Is" -Jay
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## Re: FIR filter with zero phase (no phase shift)

Like this? AFAIK a fir filter is just a specific kind of convolution. The coefficients used to convolute are not specific to LabVIEW.

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## Re: FIR filter with zero phase (no phase shift)

Interesting reply with wow's and  oohs!.  Just found a solution else where. Thanks 🙂

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## Re: FIR filter with zero phase (no phase shift)

It's a MATLAB solution, not sure it helps here. Anyway the syntax is  Filtfilt(Fir). Perhaps you can help further by providing the labVIEW equivalent, but since I can't find the labVIEW equivalent, my team chose to go with MATLAB 🙂

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## Re: FIR filter with zero phase (no phase shift)

It will help someone someday. Thanks.

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## Re: FIR filter with zero phase (no phase shift)

Absolutely. Unfortunately not all responses are helpful 🙂

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## Re: FIR filter with zero phase (no phase shift)

Sad that nobody spent 2 minutes to look in the palettes.  It took me less than 30 seconds to find this VI in the Signal Processing->Filters palette: Zero Phase Filter VI.  It looks like it behaves exactly like that Matlab function.

There are only two ways to tell somebody thanks: Kudos and Marked Solutions
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## Re: FIR filter with zero phase (no phase shift)

Thanks. I am already aware of the zero phase filter vi ( I actually hoped some of the first responders would have atleast mentioned that and then more :))

I guess what I need to know is how to generate and feed in the forward and reverse co-efficients to the zero phase filter vi. Possibly from the outputs of an FiR filter.  I am not sure the  MATLAb function is just a zero phase filter function. It looks like zero phase filtering done after applying an FIR filter. I also observed that labVIEW seems to have edge effects here the first one or two points greatly differ from the original function ( similarly the last two points)

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