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.

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  • $\begingroup$ How can I avoid that? I mean how can I make it get saturated? $\endgroup$ – Hitman 47 Dec 25 '18 at 18:41
  • $\begingroup$ Are you asking how you can maintain a constant output power in band as the input power keeps increasing? This can be done with a output power control loop; where you couple off some of the output power passed through a bandpass filter for your frequency band of interest, and then fed into a power detector which is the feedback for a leveling loop, controlling the gain in the transmit signal path. This if done properly will keep the amplifier from "clipping" your signal, which is causing the nonlinear distortion you are seeing. $\endgroup$ – Dan Boschen Dec 25 '18 at 19:40
  • $\begingroup$ But basically attenuating your input signal as much as you are increasing it such that the final power amplifier (if it is not the gain controlled component) is seeing a constant input signal above a certain input level, resulting in a constant output signal. $\endgroup$ – Dan Boschen Dec 25 '18 at 19:42

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