What is the meaning of positive phase in a bode plot?

AI Thread Summary
A Bode plot with a positive phase indicates that the output signal can lead the input signal in a steady-state relationship, which is a common characteristic of certain systems. The phase shift in Bode plots reflects the steady-state behavior of sinusoidal inputs rather than time-domain signals starting from t=0. The discussion highlights the importance of understanding that Bode plots represent the relationship between input and output in terms of frequency response, not time response. The confusion arises from interpreting phase in a time-domain context rather than a frequency-domain perspective. Overall, Bode plots are essential for analyzing system behavior in control theory and signal processing.
kandelabr
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Homework Statement


I have a bode plot with a positive phase.

Homework Equations


this is a MATLAB code for the thing
Code:
% bode phase plot
w = logspace(1, 4, 100);
G = 100*(1+0.017i*w)./(1i.*w.*(1+0.05i.*w).*(1+0.0025i.*w).*(1+0.001i.*w));
fi = atand(imag(G)./real(G));
semilogx(w, fi); % x-axis: log(omega*j), y-axis: phase in degrees

The Attempt at a Solution


Nothing to solve, there's just one thing I don't get: if phase means "relation between input and output signal", how can output signal come before the input?
 
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Keep in mind that the signals being compared are not starting from some t=0. They are a depiction of some steady-state relationship between theoretically eternal sinusoids, and as such can exhibit a relative phase shift.
 
yeah, i thought this would be the explanation, and i neglected that bode plot is steady-state only.

thanks!
 

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