apply an arbitrary shape filter to filter a time signal

[Ian_Ren]

How do I use an arbitrary shape low pass filter from the Digital Filter Design Toolkit to file a time signal/waveform?

Thanks.

Ian

[mikeporter]

Well, you could unbundle the Y data from the waveform, filter it and then insert it back into the waveform.

Mike...

[Ian_Ren]

Mike,

Thanks for your reply.

This may be a trivial question. What I meant was that after I get the "filter out" ref from the "Arbitary Shape Lawpass Foilter Design" vi, how to use this "filter out" ref to filter a waveform (or an array of data). I know it must be there, but I just cannot find any vi or node to do it.

Can you attach a screenshot or a sample vi.

Thanks.

Ian

[Ian_Ren]

In the "filter out" object of "Arbitary Shape Lowpass Filter Design" vi,  does the

"coef a (k) corresponds to "Reverse Coeefficients" of an IIR filter

and

"coef b (v)" corresponds to "Forward Coefficients" of an IIR filter or "FIR coefficients" of an FIR filter

Thanks.

Ian

[RoxtheFox]

Hi Ian,

Can you attach a snippet of your code and the VI you are specifically referencing? What is your goal in this project? Are you getting any errors?

Thanks!  

[Ian_Ren]

Roxana,

I just want to create an arbitrary shape filter and use it to filter time domain signals.

Attached vi appears to work as expected, but just want to be sure I am using these VIs correctly.

The "Filter Out" object has a lot of elements, but I cannot find any documentation about them. If you do have them, please post a link.

Thanks.

Ian

[yamadj]

Hey Ian,

Your code usages seems to be correct. If you ever have questions about code usage for a VI, I would open up context help, then hover over the VI, then go to detailed help, scroll to the bottom, and most likely you'll be able to open an example from the example finder. Specifically if you go to the example for this VI it pulls up and an example called "Zero Phase Filter.vi" which shows that your usage is correct.

[Ian_Ren]

Jordan,

Thanks for confirming this.

But honestly, I do not know how I would find out specifically how to use the "filter out" object from the "help". The "filter out" object is a cluster, the input to an IIR or FIR filter is an array, and they have different names. Maybe NI can include a simple example. Anyway, a designed filter is for filtering time signals, right? 

Thanks.

Ian

[yamadj]

Hello Ian,

Try looking up the "Analyze Frequency Response of Filter.vi" example. The filter out node is used to pass information between multiple VIs. In this example we are making a filter using the DFD Classical Design.vi, then we pass that info to two other VIs.