Does the bode function automatically converts the vector points into decibels?

I already calculated the transfer function (Vout/Vin) and I need to plot it on in a bode plot. Would I have to do the manual calculations to change it to decibels or does the bode function automatically do that?

Answer 1

[Carla]

The bode function of Control System Toolbox will plot the frequency response of a transfer function in dB. The function can also return numerical data of the magnitude of the response, and that it returns in absolute units, not dB. So, for example:

% create transfer function
H = tf([1 0.1 7.5],[1 0.12 9 0 0]);

% plot the frequency response - not the magnitude is in dB
bode(H)

% extract the magnitude data
[mag,phase,freqs]= bode(H);
% mag contains the responses at freqs, expressed in absolute units.

% convert to dB
magdb = 20*log10(mag);

See the reference page for more details.

doc bode

[Azzi Abdelmalek]

H = tf(100,[1 10]);
[mag,phase,freqs]= bode(H)
figure
subplot(2,1,1),plot(log10(freqs),20*log10(squeeze(mag)))
subplot(2,1,2),plot(log10(freqs),squeeze(phase))