Frequency response of a filter

[Shweta_Sridhar]

I have the filter coefficients of the filter I require in my program. I need to find the frequency response of this filter. Is there any function in LabVIEW that helps me to do this?

I guess I need a function which is similar to the freqz function in matlab for this.

[Tropo]

Why not search throught the LabVIEW examples for "frequency" or right click on the block diagram and select search and write "frequency"?

It all depends on which LabVIEW type you have and version. 

[Pladio]

Go on your block diagram. Then on Help there's Find Examples. On it you can search for things you need. If you search for Filter, Filter Response or Frequency Response, you can find a few examples that suit your needs.

[Shweta_Sridhar]

I went through them. 
The problem is that all those examples use the lower cut-off frequency and higher cut-off frequency as filter specifications.

I have the filter coefficients. 

Is there a way to find the frequency response of the filter whose specifications are given by its coefficients?

[Pladio]

What coefficients are you talking about ?

[Shweta_Sridhar]

The coefficients of the polynomials of the numerator and the denominator of the transfer function of the filter. 

[Tropo]

Check the example IIR Filter Design. Or the IIR Filtering and response.

Yes, the inputs the are various frequencies, ripple, and such, but if you dig into that VI you'll see that they feed those inputs to a VI which puts out the coefficients. (I.e. Butterworth filter->Butterworth coefficients).  Now, you already have your coefficients, so you just go on from there. 

[Pladio]

There's an example for that too. It's called "CDEx Gain and Phase with Frequency Data". I found it by searching for "phase response".

[Shweta_Sridhar · Accepted solution]

Thank you guys!  I found out what I wanted. But thanks for guiding me.

I'll post the answer so that others can use it 

First I found out the transfer function ( from the filter coefficients) of the filter by using:

Digital Filter Design toolkit => Utilities => From TF ( DFD Build Filter from Transfer Function.vi)

The output filter got from this was wired as the input filter to:

Digital Filter Design toolkit => Filter Analysis => Freq resp ( DFD Plot Freq Response.vi)

I got the required frequency response 🙂 :).

@Sd.Kfz.10 I coudn't use the FIR filter and IIR filter where coefficients are given as inputs (in signal processing toolkit)  because I wanted the response of the filter alone. These FIR and IIR filter requires the input signal array. 

I was using this for the linear predictive coding for speech recognition. I modelled the vocal tract as a autoregressive model (all pole filter) using a the AR modelling.vi in the ADSP toolkit. I wanted to see the frequency response of the modelled filter but I only had the filter coefficients.