Matlab code calculation error

Hello,

I am trying to calculate the width of a bandpass filter with matlab code but I am coming up with the wrong calculation and I am not sure what I need to change in my matlab code to get the right calculation.

This is the code I am using below

L = 51;
wc=0.2*pi;
Beta=1;
nn=0:(L-1); % filter length
hh=Beta*cos(wc*nn); % filter impulse response , 2/L+1
ww=0:(pi/500):(0.5*pi);
HH=freqz(hh,1,ww);
max_mag = max(abs(HH));
Beta = 1/max_mag;
hh=Beta*cos(wc*nn);
HH=freqz(hh,1,ww);

Half_max_mag = abs(HH)/sqrt(2);
xlabel('Normalized radian frequency')
jkl=find(abs(HH)>=Half_max_mag);
w2 = max(ww(jkl))
w1 = min(ww(jkl))
bandwidth = w2-w1
figure(2)
subplot(2,1,1);
plot(ww/pi,abs(HH))
yline(max(abs(HH))/sqrt(2), '--g', '3db points')
xline(w1/pi, '--r', 'w1');
xline(w2/pi, '--b', 'w2');
subplot(2,1,2);
plot(ww/pi,angle(HH))

These are the Values I am getting with this code below.

W1 = 0

W2 = 1.5708

bandwidth = 1.5708

These are the Values I am supposed to be getting with this code below but I am not getting them and I can't figure out what code to change to get that happen.

W1 = 0.5777

W2 = 0.6842

bandwidth = 0.1065

Answer 1

[AH]

Change this line Half_max_mag = abs(HH)/sqrt(2); to Half_max_mag = max(abs(HH))/sqrt(2);

[Jacob]

That worked Thank you!