Title :
Complexity of DPD linearization in the full RF-band for a WiMAX power amplifier
Author :
Wolff, Nikolai ; Bengtsson, Olof ; Heinrich, Wolfgang
Author_Institution :
Leibniz-Inst. fur Hochstfrequenztechnik, Ferdinand-Braun-Inst. (FBH), Berlin, Germany
Abstract :
In this paper, the influence of channel frequency in the RF-band on digital predistortion (DPD) is investigated empirically. A class-AB GaN-HEMT power amplifier targeting the 3.5 GHz band for WiMAX is used with a 20 MHz OFDM signal. It is found that frequency dependent memory effects in the band have a strong impact on the amount of memory taps needed for the DPD predistorter model. The overall characteristic is dominated by the non-linear behavior of the transistor, the memory effects, and the IQ imbalance introduced by the low cost modulation hardware. Using DPD models with memory that can handle IQ imbalance the EVM is improved by at least 12 dB in backed-off operation.
Keywords :
HEMT circuits; III-V semiconductors; OFDM modulation; WiMax; gallium compounds; linearisation techniques; microwave power amplifiers; wide band gap semiconductors; DPD linearization; DPD predistorter model; EVM; GaN; IQ imbalance; OFDM signal; WiMAX power amplifier; channel frequency influence; class-AB GaN-HEMT power amplifier; frequency 3.5 GHz; low cost modulation hardware; Frequency measurement; Impedance; Mathematical model; OFDM; Power amplifiers; Transistors; WiMAX; GaN-HEMT; IQ-imbalances; RF-power; WiMAX; linearization; memory effects; power amplifier;
Conference_Titel :
Microwave Conference (GeMiC), 2015 German
Conference_Location :
Nuremberg
DOI :
10.1109/GEMIC.2015.7107740
