Agilent-Circuit Envelope Simulation

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Circuit Envelope assumes that the signal can be expressed in time domain as the productof an envelope and a carrier. In frequency domain, the spectrum of the carrier is adiscrete grid of frequency components. The spectrum of the envelope is continuous in alimited bandwidth around each frequency component of the carrier.

Normally, CircuitEnvelope is more efficient than a broadband Transient when the envelope spectra atadjacent carrier frequency components do not overlap. Otherwise, the broadbandTransient or SPICE would be a better alternative. Although there are sporadic cases withoverlapping spectra where Circuit Envelope still works better than a Transient, CircuitEnvelope is not generally recommended for overlapping spectra. Particularly, when thereis an oscillator involved, overlapping spectra might cause convergence problems.

Also,envelope noise is not rigorously correct when envelope spectra overlap, because noise inthe overlapping spectra is double counted.