Limitation of Circuit Envelope Simulation

Circuit Envelope contains the following limitation:

Circuit Envelope assumes that the signal can be expressed in time domain as the product of an envelope and a carrier. In frequency domain, the spectrum of the carrier is a discrete grid of frequency components. The spectrum of the envelope is continuous in a limited bandwidth around each frequency component of the carrier. Normally, Circuit Envelope is more efficient than a broadband Transient when the envelope spectra at adjacent carrier frequency components do not overlap. Otherwise, the broadband Transient or SPICE would be a better alternative. Although there are sporadic cases with overlapping spectra where Circuit Envelope still works better than a Transient, Circuit Envelope is not generally recommended for overlapping spectra. Particularly, when there is an oscillator involved, overlapping spectra might cause convergence problems. Also, envelope noise is not rigorously correct when envelope spectra overlap, because noise in the overlapping spectra is double counted.