Butterworth filter without phase shift

[pengxin]

Hi 

I would like to design a butterworth filter of order 6 without a phase shift to my signal. A cutoff frequency of 500 Hz was chosen with a sampling frequency of 10K Hz   

[pengxin]

Please Advice me on this. Thank you

[ade77]

1. if you have the digital filter design toolkit, then you will see a butterworth VI in the function palette.

2. If you are using the student version, that comes with digital filter design toolkit.

3. right click the block diagram , signal processing, digital filters , design, IIR, butterworth.

4. or use the express classical filter design: same as (3), after design choose classical filter design.

Try to design something, then post back

[pengxin]

HI Thank you for your quick response.

I should have stated the main problem is the phase shift. I do not want this to happen. I do not see any functions that could let me to compensate for this phase shift. Could you advise me again

Thank you 

[ade77]

You might have to educate me on this "no phase shift".

 Firstly, most analog and digital filters introduce some phase shift.

Now if you want to implement constant or linear phase shift, then you might be talking of FIR filter. Like a symmetric FIR filter might be a good idea

Your design wants butterworth which is IIR, which generally have more complex phase shift.

Perhaps if you can tell me the theory behind implementing a "no phase shift" using IIR, then I might be able to chip in.

[pengxin]

Hi .I have realize i need to include a zero phase filter VI after my Butterworth filter. Let me try this first . If it succeed, I would close this thread.

[pengxin · Accepted solution]

 Solved!!! Thank you ADE77

[khan;;;;;;;;;;;;;;;;]

sir can you guide me

 iam also trying to filter a signal

after filtering i am getting amplitude of signal correctly but phase is changing a lot.

if i use Zero phase filter phase shift iam getting exactly but amplitude is not getting after filtering

how can i get both exactly....

[data acquisation]

nice solusion thanks useful for real time control

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