Experimental performance of an adaptive digital linearized power amplifier

The authors present experimental results in which an adaptive complex gain predistorter achieved a reduction in out-of-band spectral emissions in excess of 20 dB for a class AB amplifier operating close to saturation. The experimental results demonstrate that a class AB power amplifier may be linearized without sacrificing efficiency. Although significant spectral reduction was achieved in the adjacent channel, the out-of-band spectral floor was flat and approximately -50 dB from the inband spectra. The complex gain predistorter exhibits two distinct advantages: a design engineer is not forced to back off a power amplifier to its linear but highly inefficient operating point; and adaptive correction allows the effects of frequency changes, drift in bias, operating point, aging and thermal stress to be readily compensated.<
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