Presentation on Digital Predistortion of Power Amplifiers - Agilent ...
Presentation on Digital Predistortion of Power Amplifiers - Agilent ...
Presentation on Digital Predistortion of Power Amplifiers - Agilent ...
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<strong>Digital</strong> Predistorti<strong>on</strong> - 8<br />
<strong>Digital</strong> Predistorti<strong>on</strong><br />
<strong>Digital</strong> Domain<br />
Analog Domain<br />
Data<br />
Modem<br />
Complex Gain<br />
Predistorter<br />
D<br />
A<br />
C<br />
Quadrature<br />
Modulator<br />
<strong>Power</strong><br />
Amplifier<br />
Adaptati<strong>on</strong><br />
A<br />
D<br />
C<br />
Quadrature<br />
Demodulator<br />
Local<br />
Oscillator<br />
<strong>Digital</strong> Predistorti<strong>on</strong> <strong>of</strong> <strong>Power</strong> Amps<br />
June, 01<br />
FeedForward Linearizati<strong>on</strong><br />
Page 8<br />
This slide illustrates the s<strong>of</strong>tware/hardware boundary for the adaptive linearizati<strong>on</strong> circuit.<br />
In additi<strong>on</strong> to a <strong>Power</strong> Amplifier, it also requires a coupler, quadrature modulator and<br />
demodulator as well as an A/D and D/A c<strong>on</strong>verter. Note that the same oscillator is used in<br />
the Up and Down c<strong>on</strong>versi<strong>on</strong> for coherence, some methods require a phase shifter for<br />
achieving stability. The linearizer creates a predistorted versi<strong>on</strong> <strong>of</strong> the desired modulati<strong>on</strong>.<br />
The predistorter c<strong>on</strong>sists <strong>of</strong> a complex gain adjuster which c<strong>on</strong>trols the amplitude and<br />
phase <strong>of</strong> the input signal. The amount <strong>of</strong> predistorti<strong>on</strong> is c<strong>on</strong>trolled by the entries <strong>of</strong> a<br />
Look-up Table that interpolate the AM/AM and AM/PM n<strong>on</strong>linearities <strong>of</strong> the power<br />
amplifier. Note that the envelope <strong>of</strong> the input signal is an input to the Look-up table. The<br />
feedback path samples the distorted signal for which the DSP adjusts the Look-up Table<br />
entries so as to minimize the level <strong>of</strong> distorti<strong>on</strong>.
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