I want to take filtered signal have a frequency band [90 kHz to 450 kHz] from a noisy signal (in time series format) with Fs = 50 ks/s in MATLAB using following code
d1 = fdesign.highpass('N,F3dB',4,90e3,Fs);Hd = design(d1,'butter');O/P = filter(Hd,I/P);
d2 = fdesign.lowpass('N,F3dB',4,450e3,Fs);Hd = design(d2,'butter');O/P = filter(Hd,O/P);
Can anybody tell me if it is correct or not?
Hi Partha,
first of all if your sampling rate is 50kHz, you'll be able to 'see' frequencies between 0 and 25kHz (Fs/2 cf. Shannon). With that said you can generate directly a bandpass filter within matlab. If you have the fdatool it is perfect, if not just modify the parameters in the following matlab scripts:
Fs = 50000; % Sampling Frequency
Fstop1 = 10000; % First Stopband Frequency
Fpass1 = 12000; % First Passband Frequency
Fpass2 = 15000; % Second Passband Frequency
Fstop2 = 20000; % Second Stopband Frequency
Astop1 = 60; % First Stopband Attenuation (dB)
Apass = 1; % Passband Ripple (dB)
Astop2 = 80; % Second Stopband Attenuation (dB)
match = 'stopband'; % Band to match exactly
% Construct an FDESIGN object and call its BUTTER method.
h = fdesign.bandpass(Fstop1, Fpass1, Fpass2, Fstop2, Astop1, Apass, ...
Astop2, Fs);
Hd = design(h, 'butter', 'MatchExactly', match);
Regards
Olivier
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