bw = noisebw(num, den, numsamp,
bw = noisebw(num, den, numsamp, Fs) returns the two-sided equivalent noise bandwidth, in Hz, of a digital lowpass filter given in descending powers of z by numerator vector num and denominator vector den. The bandwidth is calculated over numsamp samples of the impulse response. Fs is the sampling rate of the signal that the filter would process; this is used as a scaling factor to convert a normalized unitless quantity into a bandwidth in Hz.
This example computes the equivalent noise bandwidth of a Butterworth filter over 100 samples of the impulse response.
Fs = 16; % Sampling rate Fnyq = Fs/2; % Nyquist frequency Fc = 0.5; % Carrier frequency [num,den] = butter(2,Fc/Fnyq); % Butterworth filter bw = noisebw(num,den,100,Fs)
The output is below.
bw = 1.1049