How to use the measure command in filter design

Hi!

I am trying to use the measure command to store the filter properties in a variable so that i can refer to it for comparison with other filters. Here is my code:

hd = dfilt.dffir(FVr_temp); % designs the filter for the given coefficients

m=measure(hd);

 if(m.astop==as)    
     S_struct.term=1;
 end

The m.astop is not working but I did see it being used in some code. I want to access the passband and stop frequencies and attenuations and compare them with given values. How can I do it?

Also if measure cannot be used, then what is the alternate method.

Thanks

Answer 1

[Honglei Chen]

You need to go through the fdesign interface so measure() can work. Otherwise, if you simply specify the filter coefficients, it does not know what the specification is and thus cannot perform the measurements. You can find this info and some examples in the following reference page

http://www.mathworks.com/help/dsp/ref/measure.html

HTH

[Saumya]

Oh thank you I got it. But the problem is that I am only available with the filter coefficients in my algorithm. Is there any substitute to measure command. I mean after I get h from dfilt.dffir, can I use some other command to access the properties of the filter?

Answer 2

[Saumya]

Can somebody please help!

My doubt is that I have only filter coefficients available with me. Now I have to create the FIR filter and compare its properties like passband & stopband frequencies and attenuation, with the given values. I cannot use fdesign.lowpass and measure. So, what is the alternate method?

[Honglei Chen]

compare it to what? If you know the spec, then you can just plug in the expected frequency and see if the response matches what it should be.