Hi All,
I have a time-depended signal (vector signal.mat and time.mat). In particular, I know the signal values are accelerations, sampled at 200 Hz and the signal is a real machine output so it contains noise.
My aim is to go from the time domain to the frequency domain, to see the spectrum and "later" to filter the data from the noise.
So, I wish to plot my signal amplitude and phase in the frequency domain and for this I have use the FFT function.
However, I think I did something wrong as I am expecting the signal amplitude in the frequency domain should be in the same range as is the time domain. (For example, if my object accelerates at a max of 5.5 m/s^2 in the time domain, then the same max value should be seen in the frequency domain) But, as you can see from the plots attached, the max acceleration in the time domain is about 5.5 m/s^2. But in the frequency domain the max amplitude is about 200 m/s^2.
That CANNOT BE RIGHT? right????
Below I attached my code so far. Please help me if you can
PS: I am not a great matlab user so please try to think that I am new to this software
Thanks in advance
load('time.mat');
load('signal.mat');
figure(1)
plot(time,signal);
title('Plot of the signal in the Time Domain')
xlabel('time (sec) ')
ylabel('m/s^2')
grid on
DFT_signal = fft(signal);
N = length(time);
ts = time(2)-time(1);
fs = 1/ts;
fuF = fs/N;
f = [0:fuF:(fs-fuF)/2]';
MAG_DFT = abs(DFT_signal(1:N/2));
PHASE_DFT = imag(DFT_signal(1:N/2));
subplot(2,1,1)
plot(f,MAG_DFT);
title('Plot of the Signal DFT Magnitude in the Frequency Domain')
xlabel('Frequency (Hz) ')
ylabel('m/s^2')
grid on
subplot(2,1,2)
plot(f,PHASE_DFT/pi()*180);
title('Plot of the Signal DFT Phase in the Frequency Domain')
xlabel('Phase (rad)')
ylabel('m/s^2')
grid on
