I have modelled a power amplifier using weiner's model in matlab. But when I finally plotted the input vs output power plot I got a plot that grows linear , then reaches maxima and then starts falling. As far as I know it should saturate after certain input power. Could someone tell me the reason for such behaviour? The input signal I am using is 20MHz LTE signal.
I would assume that you are only monitoring the power in-band, and what is then occurring as the signal goes into saturation is that power is being translated to other frequencies due to the non-linearity. I would suspect that this would dominantly be power in harmonic frequency locations, notably the third and fifth harmonics.