Title :
Fast predistorter adaptation to varying antenna load
Author :
Nielsen, Troels S. ; Lindfors, Saska
Author_Institution :
RF Integrated Syst. & Circuits (RISC) Div., Aalborg Univ., Denmark
Abstract :
The effect of varying power amplifier (PA) output VSWR is studied in a workfunction predistorter system. The resistive load of a commercially available W-CDMA PA is tuned and the large-signal S-parameters measured. From the measurements, the optimum gain and phase predistortion functions are derived and studied. The predistorter coefficients are parameterized with a single variable that roughly fits optimum predistortion functions for other than nominal PA loading conditions. The adaptation speed is evaluated in a complete predistorter system simulator and it is found that the number of iterations needed to adapt is reduced from 4 to 1.
Keywords :
3G mobile communication; S-parameters; UHF antennas; UHF power amplifiers; cellular radio; iterative methods; mobile antennas; mobile handsets; nonlinear distortion; phase estimation; VSWR; W-CDMA PA; adaptation speed; fast predistorter adaptation; iterations; large-signal S-parameters; optimum gain; phase predistortion; power amplifier output; varying antenna load; workfunction predistorter system; Adaptive arrays; Adaptive systems; Gain measurement; Loaded antennas; Multiaccess communication; Phase measurement; Power amplifiers; Predistortion; Scattering parameters; Voltage;
Conference_Titel :
Vehicular Technology Conference, 2004. VTC 2004-Spring. 2004 IEEE 59th
Print_ISBN :
0-7803-8255-2
DOI :
10.1109/VETECS.2004.1387902
