Plot a bandpass filter at a central frequency F0 in MATLAB

[Saly07]

Hi,

I have this filter:

d = fdesign.pandpass('n,F3dB',3,50e3, 200e6);
Hd = design(d,'butter');

which I want to plot at a central frequency of 868.3 MHz.

Could you pleaase help me with this?

Thank you in advance!

 

[thylacine1975]

For a bandpass filter response you must specify both corner frequencies of the passband, e.g.:

d = fdesign.bandpass('N,F3dB1,F3dB2', 4, 50e3, 200e6, 2e9);

(...where I've added a 'sampling frequency' value of Fs = 2GHz for a valid digital filter implementation. The fdesign.xxx() functions have a squillion possible arguments, depending on what you're trying to do with them).
Design the filter with:

Hd = design(d,'butter');

And view the resulting transfer function with:

fvtool(Hd);