How do I assign frequency values to the obtained fft values without plotting . I need to know the value of the peak at 16Hz for further calculations.

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Yogesh 2024-4-24

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评论： Yogesh 2024-4-24

采纳的回答： vidyesh

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clear all

close all

clc

L=10;

n=1.45;

c=2.9979e8;

dt = 6e-12;

T=10*2*L*n/c;

t = (-T/2/dt:1:T/2/dt)*dt;

Nt=round(T/dt);

fsine = 1e9;

vsine = 1;

phi = vsine*sin(2*pi*fsine*t);

EL1t=1.274e7*exp(1i*phi);

FP=fft(phi);

fs=1/dt/Nt;

Fs=(-1/dt/2:fs:1/dt/2-1);

Z=plot(Fs,fftshift(abs(fft(EL1t))));

I need to know the value at 16GHz in the plot.

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Answer 1

vidyesh 2024-4-24

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Hi Yogesh,

You can use the max function to find the value of the peak and its index in the array.

Then use the index to get the corresponding frequency.

https://www.mathworks.com/help/matlab/ref/max.html

Add the below lines to your code.

pow = fftshift(abs(fft(EL1t)));
[val,ind] = max(pow)
f_max = Fs(ind);

Hope this helps

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vidyesh 2024-4-24

在 MATLAB Online 中打开

I thought you wanted the value at peak (max value).

You can use the below code to find the value at a specific frequency:

freq_f = 16e9;
% nnz(Fs==freq_f) % returns 0

In this case it seems like array 'Fs' doesnt contain the exact value of 16 GHz, so we find the closest value.

[val,ind] = min(abs(Fs-freq_f)); % Find freq closest to 16 GHz
disp(Fs(ind));
disp(pow(ind));

Yogesh 2024-4-24

Thank you Vidyesh , you were really helpful...

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How do I assign frequency values to the obtained fft values without plotting . I need to know the value of the peak at 16Hz for further calculations.

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