I have a power density plot with the below matlab code. I want to find the 3dB bandwidth of it. Can someone help me to solve this matter

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SriMiGSS 2018-1-23

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编辑： Sai Charan Sampara 2022-6-28

%%PARAMETERS
D = 1*10^6;     
vi = 10^6;      
r = 10^4;       
%%RANGE
w = linspace(0.9*10^6,1.1*10^6,211);
%%EQUATION
b = 0.7;
syms m n;
Y1 = (((D/(4.*b))^m)*((2*m.*b)+(r/2)))./(factorial(m)*(((2*m.*b)+(r/2))^2+(w-vi).^2));
Y = symsum(Y1, m, 0, 10);
%%PLOT
plot(w-vi,Y,'blue');
xlabel('Frequency Detuning (Hz)');
ylabel ('Relative Power Density');

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Answer 1

Sai Charan Sampara 2022-6-28

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编辑：Sai Charan Sampara 2022-6-28

Convert the power density into logarithm scale. Use the max function to find the maximum power density in dB. The value of (maximum-3) dB is cut off power density value. Then use the logical equation index=frequency==maximum-3 to get the indices of the frequency values. There should be two values of frequency for which this holds true. Both the upper and lower cut off frequencies can be accessed by frequency(index). Their difference gives 3dB bandwidth in Hertz.