TY - JOUR
T1 - Circuits and system design of RF polar transmitters using envelope-tracking and SiGe power amplifiers for mobile WiMAX
AU - Li, Yan
AU - Lopez, Jerry
AU - Lie, Donald Y.C.
AU - Chen, Kevin
AU - Wu, Stanley
AU - Yang, Tzu Yi
AU - Ma, Gin Kou
N1 - Funding Information:
Mr. Lopez was the recipient of a Northrop Grumman Fellowship and an NSF Educational Fellowship.
PY - 2011
Y1 - 2011
N2 - This paper discusses the circuits and system design methodology of a highly-efficient wideband RF polar transmitter (TX) using the envelope-tracking (ET) technique for mobile WiMAX applications. Monolithic power amplifiers (PAs) are designed and fabricated in IBM 0.18 μm SiGe BiCMOS technology, and a linear-assisted witch-mode envelope amplifier is applied to modulate the PA supply voltage to form the core of the RF polar TX. Nonlinearities caused by bandwidth limitation of the envelope amplifier and timing misalignment have been investigated. When driven by WiMAX 64QAM 8.75 MHz signals, the overall PAE of our ET-based polar TX system reaches 30.5% at 17 dBm average output power, while also meeting the stringent WiMAX linearity specs without using any predistortion. When the decresting algorithm using the soft limiter is applied to the baseband, the overall PAE increases to 33%, at the expense of a higher EVM of 4.9%. Based on measurement results, our ET-based polar TX system has demonstrated excellent efficiency with good linearity for high peak-to-average ratio (PAR) broadband signals when compared with the recent literature on state-of-the-arts polar TX designs.
AB - This paper discusses the circuits and system design methodology of a highly-efficient wideband RF polar transmitter (TX) using the envelope-tracking (ET) technique for mobile WiMAX applications. Monolithic power amplifiers (PAs) are designed and fabricated in IBM 0.18 μm SiGe BiCMOS technology, and a linear-assisted witch-mode envelope amplifier is applied to modulate the PA supply voltage to form the core of the RF polar TX. Nonlinearities caused by bandwidth limitation of the envelope amplifier and timing misalignment have been investigated. When driven by WiMAX 64QAM 8.75 MHz signals, the overall PAE of our ET-based polar TX system reaches 30.5% at 17 dBm average output power, while also meeting the stringent WiMAX linearity specs without using any predistortion. When the decresting algorithm using the soft limiter is applied to the baseband, the overall PAE increases to 33%, at the expense of a higher EVM of 4.9%. Based on measurement results, our ET-based polar TX system has demonstrated excellent efficiency with good linearity for high peak-to-average ratio (PAR) broadband signals when compared with the recent literature on state-of-the-arts polar TX designs.
KW - Decresting algorithm
KW - SiGe power amplifier (PA)
KW - envelope-tracking (ET)
KW - linear-assisted switch mode envelope amplifier
KW - polar transmitters
KW - power-added efficiency (PAE)
UR - http://www.scopus.com/inward/record.url?scp=79955522040&partnerID=8YFLogxK
U2 - 10.1109/TCSI.2010.2089562
DO - 10.1109/TCSI.2010.2089562
M3 - Article
AN - SCOPUS:79955522040
SN - 1549-8328
VL - 58
SP - 893
EP - 901
JO - IEEE Transactions on Circuits and Systems I: Regular Papers
JF - IEEE Transactions on Circuits and Systems I: Regular Papers
IS - 5
M1 - 5648389
ER -