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Frequency Response of Lowpass Bessel Filter

Design a fifth-order analog lowpass Bessel filter with approximately constant group delay up to 104 rad/second. Plot the magnitude and phase responses of the filter using freqs.

[b,a] = besself(5,10000);

Figure contains 2 axes objects. Axes object 1 with xlabel Frequency (rad/s), ylabel Phase (degrees) contains an object of type line. Axes object 2 with xlabel Frequency (rad/s), ylabel Magnitude contains an object of type line.

Compute the group delay response of the filter as the derivative of the unwrapped phase response. Plot the group delay to verify that it is approximately constant up to the cutoff frequency.

[h,w] = freqs(b,a,1000);
grpdel = diff(unwrap(angle(h)))./diff(w);

xlabel('Frequency (rad/s)')
ylabel('Group delay (s)')

Figure contains an axes object. The axes object with xlabel Frequency (rad/s), ylabel Group delay (s) contains an object of type line.

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