SKEDSOFT

Phase angle of quadratic factor

The phase angle is a function of both ω and At ω = 0, the phase angle equals 0°. At the corner frequency ω = ω_n, the phase angle is -90° regardless of since

At ω = ∞, the phase angle becomes -180°. The phase-angle curve is skew symmetric about the inflection point, the point where Φ = -90°. There are no simple ways to sketch such phase curves. We need to refer to the phase-angle curves shown in Figure.

The frequency-response curves for the factor

can be obtained by merely reversing the sign of the log magnitude and that of the phase angle of the factor

To obtain the frequency-response curves of a given quadratic transfer function, we must first determine the value of the corner frequency ω_n and that of the damping ratio . Then, by using the family of curves given in Figure, the frequency-response curves can be plotted.