The plot shows W, the continuous-time maximum loop gain that you specified, as a dashed
line. The shaded region shows the discretized version of W that systune uses for tuning.
The discretized maximum loop gain cuts off at the Nyquist frequency corresponding to
the sample time of CL. Near that cutoff, the shaded region diverges from the dashed line.
The plot highlights that sometimes it is preferable to specify tuning goals for discrete-
time tuning using discrete-time gain profiles. In particular, specifying a discrete-time
profile gives you more control over the behavior of the gain profile near the Nyquist
frequency.
Visualize Tuning Goals