Analysis and design of a dynamic predistorter for WCDMA handset power amplifiers

作者：Yamanouchi Shingo^*; Aoki Yuuichi; Kunihiro Kazuaki; Hirayama Tomohisa; Miyazaki Takashi; Hida Hikaru

来源：IEEE Transactions on Microwave Theory and Techniques, 2007, 55(3): 493-503.

DOI：10.1109/TMTT.2006.890515

• adjacent channel leakage power ratio (ACPR)
• intermodulation distortion (IMD)
• linearization
• nonlinear distortion
• power amplifiers (PAs)
• predistorter (PD)

This paper presents a dynamic predistorter (PD), which linearizes the dynamic AM-AM and AM-PM of a wide-band code division multiple access handset power amplifier (PA). The dynamic PD allows an adjacent channel leakage power ratio (ACPR) improvement of 15.7 dB, which is superior to conventional PDs that linearize static AM-AM and AM-PM. The dynamic PD was designed using an HBT generating nonlinearity, a short circuit at the baseband (<= 4 MHz), and a load circuit for the HBT at the RF fundamental band (approximate to 1.95 GHz). Volterra-series analysis was performed to understand the mechanism of the dynamic PD. The analysis revealed that the short circuit at the baseband enabled the dynamic PD generating third-order intermodulation distortion (IMD3) with opposite phase to the fundamental tone (i.e., antiphase IMAD3). The antiphase IMD3 allows dynamic gain compression, which linearizes the dynamic gain expansion of a PA with low quiescent current. The analysis also revealed that the IMD3 amplitude of the dynamic PD can be adjusted by load impedance at the RF fundamental band, which enables the gradient of dynamic AM-AM and AM-PM to be optimized to linearize the PA. The fabricated two-stage InGaP/GaAs HBT PA module with the dynamic PD exhibited an ACPR of -40 dBc and a power-added efficiency of 50% at an average output power of 26.8 dBm with a quiescent current of 20 mA.

• 出版日期2007-3