Presentation on RF Predistortion of Power Amplifiers - Agilent ...
Presentation on RF Predistortion of Power Amplifiers - Agilent ...
Presentation on RF Predistortion of Power Amplifiers - Agilent ...
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<strong>RF</strong>-Based Predistorti<strong>on</strong><br />
<strong>Power</strong> Amplifier<br />
<strong>RF</strong> input<br />
Delay<br />
Complex Gain<br />
Adjuster<br />
<strong>RF</strong> Output<br />
I<br />
Q<br />
Envelope Detector<br />
Work Functi<strong>on</strong><br />
or Look-up<br />
Table<br />
Out <strong>of</strong> Band<br />
Filter<br />
DSP<br />
Optimizati<strong>on</strong> <strong>of</strong><br />
Parameters<br />
<strong>Power</strong> Detector<br />
5<br />
The linearizer creates a predistorted versi<strong>on</strong> <strong>of</strong> the desired modulati<strong>on</strong>. The predistorter<br />
c<strong>on</strong>sists <strong>of</strong> a complex gain adjuster that c<strong>on</strong>trols the amplitude and phase <strong>of</strong> the input<br />
signal. The amount <strong>of</strong> predistorti<strong>on</strong> is c<strong>on</strong>trolled by two n<strong>on</strong>linear work functi<strong>on</strong>s that<br />
interpolate the AM/AM and AM/PM n<strong>on</strong>linearities <strong>of</strong> the power amplifier.<br />
Note that the envelope <strong>of</strong> the input signal is an input to the work functi<strong>on</strong>s. The feedback<br />
path samples a porti<strong>on</strong> <strong>of</strong> the undesired spectrum. The work functi<strong>on</strong> parameters are<br />
then adjusted by the DSP to minimize the undesired signal. The undesired signal is<br />
typically the adjacent channel power.
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