Hello:
I am working on app designer. My app is about communications and I need to plot the frequency response of a mixer. However, the levels of signal power I'm using are lower than a reference, so I need to plot some negative amplitude levels in dB.
In the real life I need to obtain this:
but in Matlab I don´t know how to plot those negative values.
The code I'm using is this:
function spectrum(app)
%For sin signal and AM
if app.SinButton.Value == true && app.AmplitudeModulationButton.Value == true
[fc,A,Ap,fm,Fs,Ts,N,t,f,mi,Vcdol,Vcdif] = getdata(app);
x = Vcdif+A*sin(2*pi*fm*t); % IF
p= Vcdol+Ap*sin(2*pi*fc*t); % carrier signal
y=((1+mi*x).*p); %modulated signal
plot(app.UIAxes,f,10*log10(abs(fftshift(fft(y))));
