Linearisation by means of frequency retranslation [1]

The signal cancellation and error signal predistortion loops were first optimised. Then without any readjustments, the error amplifier is turned ON/OFF (twice). The system responds and converges fairly quickly.

When the error amplifier is ON and the system is closed-loop, fine-tuning of amplitude and phase settings can provide even larger IMD suppression.

References:

[1]  http://video.google.com/videoplay?docid=2067084063584550119&hl=en