I plotted my recorded signal using fftshift and got two symmetric spectrums in Matlab. How can I display half of the frequency spectrum result? Thanks

I plotted my recoded signals and got two symmetric spectrums and will like to use halve of it.

What can I do to achieve this?

dt = T_ADE(2,1)-T_ADE(1,1);

[N, M] = size(T_ADE);

fmax = 1/(2*dt);

for n =1:N

t(n)=(n-1)*dt;

f(n)=-fmax + (n-1)*df;

end

x1 = fftshift(T_ADE(:,2)); % swaps the left and right halves

X = fft(x1); X1=fftshift(X);

%Sf = fftshift(fft(T_ADE(:,2)*dt)); % Apply FFT Swap the left and right halves

figure(2)

plot(f/1e9,abs(X1), 'b', 'Linewidth',2);

xlabel('Frequency[GHz]'); ylabel('Signal Amplitude [dB]');

title('Frequency Response of the Transmitted Wave');

Answer 1

[Star Strider]

I do not have your data, so I am using only the information that you provided.

This is how I would do it:

dt = T_ADE(2,1)-T_ADE(1,1);                                     % Sampling Interval (Assuming Regular Sampling)
Fs = 1/dt;                                                      % Sampling Frequency
Fn = Fs/2;                                                      % Nyquist Frequency
L = size(T_ADE,1);                                              % Number Of Observations

ADE2_mean = mean(T_ADE(:,2));                                   % Calculate D-C Offset
FT_ADE2 = fft(T_ADE(:,2) - ADE2_mean)/L;                        % Length-Scaled Fourier Transform
Fv = linspace(0, 1, fix(L/2)+1)*Fn;                             % Frequency Vector
Iv = 1:numel(Fv);                                               % Corresponding Index Vector

figure(2)
plot(Fv, abs(FT_ADE2(Iv))*2)
grid
xlabel('Frequency (Cycles/Time Unit)')
ylabel('Amplitude (Units)')

I obviously cannot test this without your data. However this sort of approach has worked numerous times in the past, and likely will work here with your data as well.

[isa ali]

Thanks @Star Strider! It worked just I want it. I really appreciate your time and insight.

[Star Strider]

As always, my pleasure!