Assistance with Filter Code

I am looking to create a lowpass filter; however, I am not able to do it following the guidance offered by the MatLab tutorials. I need the filter to include, Fp, Fst, Ast, Fc, Ast, and N. Maybe my problem is that I am not able to use all of the specifications. I would really appreciate a jump start as I have spent days trying to work through this and I am sure that it is extremely easy for most. Thank goodness, this is the only MatLab code I will be in need of for my project. THANKS!!!

Mandy D.

[Star Strider]

What type filter are you designing, and what tools or functions are you using to design it?

I suggest you use the [z p k] and sos syntax in your design, rather than tf if you have that option.

[Honglei Chen]

Your specification is a little strange in the sense that you have both Fp, Fst and Fc. Do you mean Fs instead of Fc?

Answer 1

[Ryan G]

If you search the doc for lowpass filter you will find:

fdesign lowpass from the signal processing toolbox.

If you have access you can type in:

D = fdesign.lowpass

and you will see

Response: 'Lowpass'      
        Specification: 'Fp,Fst,Ap,Ast'
          Description: {4x1 cell}     
  NormalizedFrequency: true           
                Fpass: 0.45           
                Fstop: 0.55           
                Apass: 1              
                Astop: 60

You can then use

H = design(D)

after you setup your specs to design the filter. There are a lot more details depending on your end goal in the documentation for both design and fdesign.lowpass