How to Calculate Vertical Wavelength
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Hi,
In the attached file "Signal" I have three (3) columns of signals. Please I want to calculate the wavelength?. The dt is 0.02 km. the data ranges from 20 to 40 km.
thanks
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Star Strider
2020 年 3 月 5 日
This should get you started:
D = load('Signal.txt');
dt = 0.02;
L = size(D,1);
t = linspace(0, 1, L)*dt;
Fs = 1/dt;
Fn = Fs/2;
FTD = fft(D - mean(D))/L;
Fv = linspace(0, 1, fix(L/2)+1)*Fn;
Iv = 1:numel(Fv);
[Amax,idx] = max(abs(FTD(Iv,:))*2);
FreqAtMaxAmplitude = Fv(idx)
figure
subplot(3,1,1)
plot(Fv, abs(FTD(Iv,1))*2)
xlim([0 5])
grid
subplot(3,1,2)
plot(Fv, abs(FTD(Iv,2))*2)
grid
xlim([0 5])
subplot(3,1,3)
plot(Fv, abs(FTD(Iv,3))*2)
grid
xlim([0 5])
The wavelength is the propagation velocity divided by the frequency in radians/time unit. The ‘FreqAtMaxAmplitude’ gives the frequencies of the peaks in Hz, so multiply these by to get the radian frequencies. You will then have to provide the propagation velocity in order to calculate the wavelength:
lambda = propagation_velocity ./ (2*pi*FreqAtMaxAmplitude)
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