Bandpass FIR filter labview

1
votes

I am trying to make a bandpass FIR filter in Labview. I have created two sine waves (one with freq = 1Hz, amplitude = 1 and the second with freq=50, amplitude = 0.1) that I added together. Input signal

And now I want to create a bandpass filter to filter out the 50Hz signal (I know that its possible use just low pass filter, but I need to use bandpass filter). I set the low cutoff freq to 0.01 and high cutoff freq to 3, but the result is witout any change.

enter image description hereOn top of that when I change the parameters I get no change.

When I use the butterworth filter I get the result that I am looking for. enter image description here

This is my code:

enter image description here

What am I missing?

2
filterlabviewbandpass-filter
Can you give us a snippet? - berna1111

2 Answers

1
votes

Most probably you just need to play with the settings to find the ones that suite you the most.

See the example bellow: enter image description here

And its snippet (drag and drop the image into a blank VI): enter image description here

1
votes

You say you need to use a Bandpass filter, but in your VI you are using a Bandstop filter. Not sure which of the two is the error. Just as a recap:

  • Lowpass filter passes anything below the set freq.
  • Highpass filter passes anything above the set freq.
  • Bandpass filter passes anything between the set freq.
  • Bandstop filter passes everything except the part between the set freq.

The Butterworth part has nothing to do with high, low or bandpass but with how fast the fall-off is after the set frequency.

See the image for a working vi and results. VI Snippet Graph

Hope this helps.