Here are the results of 11 experiments with sine wave inputs to a system in the lab.

The frequency ranges from 0.01 Hz to 2 Hz

On the left is the experimental time response.
The Input is the dark curve, the Output is the lighter curve.

Notice how the Output curve shifts to the right of the Input Curve as the frequency increases. This is increasing (negative) Phase Angle.

Notice how the Output curve has decreasing height (amplitude) as the frequency increases. This is decreasing Amplitude Ratio.

On the right are the Lissajous figures for each of these frequencies
Notice at VERY LOW frequencies, the Lissajous is almost a straight line; It is actually part of the SSOC.
Notice the Lissajous is symmetric, or horizontal oval, when the phase angle is about 90 degrees.
Notice when the phase angle reaches 180 degrees, the Lissajous is again a stright line. The frequency at which this occurs is the Ultimate Frequency. F=0.01
PA = 0

F=0.05
PA very small

F=0.1
PA about 10 degrees

F=0.2
PA about 60 degrees

F=.35
PA about 90 degrees

F=0.5
PA about 150 degrees

F=0.7
PA about 180 degrees

F=0.8
PA about 210 degrees

F=1
PA about 260 degrees

F=1.5
PA about 330 degrees

F=2
PA about 380 degrees