In a first step, the various envelope models are evaluated based on TWT measurements only, as this mitigates other error sources, such as inaccuracies in the underlying interaction model or its numerical implementation. In a second step, we replace the measured data by those from the steady-state simulation tool MVTRAD. This defines the proposed hybrid time- and frequency-domain approach, which combines the steady-state simulation of MVTRAD with the various envelope codes.