Mobile phone power amplifier linearity and efficiency enhancement using digital predistortion

Abstract

-The new generation mobile communication systems using spectrum efficient linear modulation schemes (QPSK, 8PSK, QAM) need linear power amplifiers in the transmission path to have good ACPR and EVM values. Linearization methods can be used to increase the linearity of the power amplifiers (PA). However, it is not reasonable to use complicated, power consuming and high cost systems. This paper presents a digital predistortion implementation for WCDMA signals using an FPGA (Field Programmable Gate Array) as DSP and investigates the application of this system in handsets. The method applied requires minimum change in the conventional transmitter path configuration but considerable PAE improvement can be achieved.

Experimental investigation on the performance degradations of the GaN class-F power amplifier under humidity conditions

“…With the rapid development of wireless communication, the increasing demands in the phased array radars [1][2][3][4], mobile communication systems [5][6][7], and satellite communication have motivated for GaN-based radio-frequency (RF) power amplifiers (PAs) [8,9]. GaN-based RF PAs are one of the key modules for a wireless communication system (WCS) comprised of the transmitting or receiving antennas [10,11], and usually preferred over GaAs and Si-based PAs due to the highpower capabilities, high breakdown voltage, and reliability in high temperature [12].…”

A GaN HEMT power amplifier with variable gate bias for envelope and phase signals

“…The output network to some extent provides filtering of the desired output frequency band. It must be noted that the characteristic from the low-frequency signal to the output is non-linear; It is assumed that pre-distortion [9] or feedback [10] is used.…”

“…Unfortunately, this amplifier structure is designed for efficiency and is far from linear, so some form of linearization will be required before the signal splitter stage. Digital Predistortion (DPD) [9] would be a potential candidate for this as it can handle wide bandwidths and memory effects can also be included.…”