Matlab Upsample Filter Object

We can create Matlab filter objects using `fdesign` then `design`

 TW    = 0.25;  % Transition Width (1/8 pass band)
 Astop = 40  ;  % Stopband Attenuation (dB)

 h   = fdesign.interpolator(2, 'Halfband', 'Type', 'Lowpass', 'tw,ast',TW,Astop);
 Hd  = design(h, 'ellip'); 

 fvtool(Hd)

How do we create a matlab filter object which just does zero insertion? The filter object equivalent of upsample, which operates on data.

NB: Sample and Hold can be modelled with a first order CIC.

Answer 1

[Puneet Rana]

Hi Morgan,

You can do this by setting Numerator of interpolator to [1,0]. For example, using the dsp.FIRInterpolator System object:

>> interp = dsp.FIRInterpolator;
>> interp.InterpolationFactor = 2;
>> interp.Numerator = [1,0];
>> x = (1:5)';
>> step(interp, x)

ans =

       1
       0
       2
       0
       3
       0
       4
       0
       5
       0