A Wideband Digital Predistorter for a Doherty Power Amplifier Using a Direct Learning Memory Effect Filter

Kenichi HORIGUCHI  Naoko MATSUNAGA  Kazuhisa YAMAUCHI  Ryoji HAYASHI  Moriyasu MIYAZAKI  Toshio NOJIMA  

Publication
IEICE TRANSACTIONS on Electronics   Vol.E93-C   No.7   pp.975-982
Publication Date: 2010/07/01
Online ISSN: 1745-1353
DOI: 10.1587/transele.E93.C.975
Print ISSN: 0916-8516
Type of Manuscript: Special Section PAPER (Special Section on Recent Progress in Microwave and Millimeter-Wave Technologies)
Category: 
Keyword: 
predistortion,  adaptive filter,  memory effect,  power amplifier,  Doherty amplifier,  

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Summary: 
This paper presents a digital predistorter with a wideband memory effect compensator for a Doherty power amplifier (PA). A simple memory-predistortion model, which consists of a look-up-table (LUT) and an adaptive filter equalizing memory effects, and a new memory effect estimation algorithm using a direct-learning architecture are proposed. The proposed estimation algorithm has an advantage that a transfer function of a feedback circuit does not affect the learning process. The predistorter is implemented in a field programmable gate array (FPGA) and a digital signal processor (DSP). The transmitter has achieved distortion level of -50.8 dBr at signal bandwidth away from the carrier, and PA module efficiency of 24% with output power of 43 dBm at 2595 MHz under a 20 MHz-bandwidth orthogonal frequency division multiplexing (OFDM) signal using laterally diffused metal oxide semiconductor (LDMOS) FETs.