When using Virtuoso ADE Calculator's DFT function, it keeps giving this warning message that the sample points are interpolated, which may cause numerical error problems. I see that the x axis of the simulation points of the signal aren't equally spaced apart, which is probably why the DFT uses interpolated points. I've tried setting the step and max step size to be the same for transient analysis(using Hspice simulator), but the x axis of the simulation points still won't be equally spaced apart. Can someone shed light on this? Thank you!