Design a Filter using the Digital FIR Filter.vi

[Getwonder]

Hello,

I was working with Digital FIR Filter.vi to create a bandstand filter.

The problem I faced is regarding the FIR Filter Specification, the Frequencies given for the Upper and Lower Pass and Stop band.

For a low pass Filter, the upper Stop Band frequency is set at 0. While the Lower Stop band frequency is set at 200.

And the Lower pass band is set at 100 while the upper pass band is set at 0.

What the lower and upper frequencies actually means? As for a low pass filter, the upper cutoff frequency must be greater than lower. 

So plus tell me how does it works and what frequencies should I specify for a Bandstand Filter.

Thanks v.much

[Sev_K]

Hi,

Lower PB is the lower of the two passband frequencies. The default is 100Hz.
Upper PB is the higher of the two passband frequencies. The default is 0.

Lower SB is the lower of the two stopband frequencies. The default is 200Hz.
Upper SB is the higher of the two stopband frequencies. The default is 0.

You are correct in a sense that the Upper PB frequency should have a greater value than the Lower PB frequency. Thus, for your application you would need to change the default values for Upper PB and Upper SB from zero to something higher than Lower PB and Upper SB, respectively.

[Getwonder]

So pls guide me what Cut off frequencies should be set for the bandpass and bandstop filter.

Thanks

[Sev_K]

Hi,

Have a look at the following example: [LabVIEW Folder]\examples\Digital Filter Design\Floating-Point Filters\Conventional\Classical Filter Design.vi .This example demonstrates how to use the DFD Classical Design VI to design a lowpass, highpass, bandpass, or bandstop filter with classical design methods.

Complete the following steps to use this VI.
1) Run the VI.
2) Change the specifications.
3) Observe the magnitude response and phase response. Notice that the magnitude response approximates the frequency specification and the phase response is nonlinear for IIR filters (Butterworth, Chebyshev, Inverse Chebyshev, and Elliptic).
4) Change the Design Method to view the ripples in the passband and stopband.
5) Observe the filter order that the VI returns automatically.
6) Click the STOP button to stop this VI.

[A_LI]

hello

 i have made a vi of iir chebyshev filter in simulated 

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@Sev_K wrote:

Hi,

Have a look at the following example: [LabVIEW Folder]\examples\Digital Filter Design\Floating-Point Filters\Conventional\Classical Filter Design.vi .This example demonstrates how to use the DFD Classical Design VI to design a lowpass, highpass, bandpass, or bandstop filter with classical design methods.

Complete the following steps to use this VI.
1) Run the VI.
2) Change the specifications.
3) Observe the magnitude response and phase response. Notice that the magnitude response approximates the frequency specification and the phase response is nonlinear for IIR filters (Butterworth, Chebyshev, Inverse Chebyshev, and Elliptic).
4) Change the Design Method to view the ripples in the passband and stopband.
5) Observe the filter order that the VI returns automatically.
6) Click the STOP button to stop this VI.

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[TheGeeze]

Is there something else you need help with? Is the filter working as you expect?

Ryan

[A_LI]

Hi Ryan

 Yes, i have developed an IIR chebyshev filter using express VIs

iam unable to validate its power spectrum output.

 i have attached my project in attachment please find the attachment 

waiting for your reply 

[A_LI]

Hi Ryan

Filter is not working properly, as there is some amount of delay and bugs also .
As iam working in Development computer with simulated i/o's.
 
Please find the attached files


Regards
Ali
A.E.