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ABSTRACT: A monolithic SiGe BiCMOS envelope-tracking power amplifier (PA) is demonstrated for 802.11g OFDM applications at 2.4 GHz. The 4-mm<sup>2</sup> die includes a high-efficiency high-precision envelope amplifier and a two-stage SiGe HBT PA for RF amplification. Off-chip digital predistortion is employed to improve EVM performance. The two-stage amplifier exhibits 12-dB gain, <5% EVM, 20-dBm OFDM output power, and an overall efficiency (including the envelope amplifier) of 28%.
IEEE Journal of Solid-State Circuits 07/2007; · 3.23 Impact Factor
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ABSTRACT: This paper discusses the design of monolithic RF broadband Class E SiGe power amplifiers (PAs) that are highly efficient and linear. Load-pull measurement data on IBM 7HP SiGe power devices have been made at 900MHz and 2.4GHz and monolithic class E PAs have been designed using these devices to achieve highest power-added-efficiency (PAE) at these frequencies. It is found that high PAE can be achieved for monolithic single-stage Class E PAs designed using high-breakdown SiGe transistors at ~65% (900MHz) and ~40% (2.4GHz), respectively, which are roughly ~10% lower than the device's maximum PAE values obtained by load-pull tests under optimal off-chip matching conditions. We have also demonstrated that monolithic SiGe class E PAs can be successfully linearized using an open-loop envelope tracking (ET) technique as their output spectra pass the stringent EDGE transmit mask with margins, achieving overall PAE of 44.4% for the linearized PA system that surpasses the < 30% PAE with commercially available GaAs Class AB PAs for EDGE applications. These promising results indicate the feasibility of realizing true single-chip wireless transceivers with on-chip RF SiGe PAs for spectrally-efficient non-constant-envelope modulation schemes
Solid-State and Integrated Circuit Technology, 2006. ICSICT '06. 8th International Conference on; 11/2006
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ABSTRACT: This paper reports on the results of a highly efficient monolithically fully-integrated SiGe Class E power amplifier using envelope tracking techniques for EDGE applications. The envelope-tracking (ET) system includes a discrete linear op-amp and a switching power converter. The RF Class E amplifier was fabricated in a 0.18 μm BiCMOS SiGe technology. The RF Class E power amplifier achieved a collector efficiency (CE) of 62.7% and the overall power added efficiency (PAE) of the ET system is 44.4% at an output power of 20.4 dBm for an 881 MHz EDGE modulated signal. A discrete envelope switching amplifier achieved 82.8% efficiency while driving the Class E PA voltage supply. The linearized SiGe PA passed the stringent EDGE transmit spectrum mask.
Radio and Wireless Symposium, 2006 IEEE; 02/2006
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ABSTRACT: This paper provides an overview of power amplifier architectures for high efficiency and linearity over a wide range of output power levels, as required in CDMA, WLAN and other mobile wireless applications. Envelope tracking and Doherty amplifiers are described and issues for their implementation with HBTs are discussed. Envelope tracking implementation issues are reviewed. A Doherty CDMA amplifier with high overall efficiency (averaged over output power levels) is presented.
Bipolar/BiCMOS Circuits and Technology Meeting, 2005. Proceedings of the; 11/2005
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ABSTRACT: An efficiency-enhanced power-amplifier system design is presented based on wide-bandwidth envelope tracking (WBET) with application to orthogonal frequency-division multiplexing wireless local area network systems. Envelope elimination and restoration (EER) and WBET are compared in terms of the time mismatch sensitivity between the base-band amplitude path and the RF path, and it is demonstrated that WBET is much less sensitive than EER to these effects. An adaptive time-alignment algorithm for the WBET system is developed and demonstrated. The analysis and algorithm are verified by experimental results. The measurement shows that the peak drain efficiency of the complete system was 30% at a 2.4-GHz orthogonal frequency-division multiplexing output power of 20 dBm.
IEEE Transactions on Microwave Theory and Techniques 05/2005; · 1.85 Impact Factor
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ABSTRACT: This paper presents a power amplifier based on envelope tracking (ET) with application to the WLAN 802.11g system. Baseband pre-distortion is implemented to improve the linearity. A high-efficiency wide-bandwidth envelope amplifier and a GaAs MESFET class AB RFPA are designed and implemented for the system. An overall system drain efficiency of 30% is obtained for an OFDM output power of 20 dBm at 2.4GHz.
Microwave Symposium Digest, 2004 IEEE MTT-S International; 07/2004
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Feipeng. Wang
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ABSTRACT: High efficiency radio frequency (RF) power amplifiers (PAs) are critical in portable battery-operated wireless communication systems because they can dominate the power consumption. Linear power amplifier is required for envelope modulated signal. Traditionally, linear power amplifiers are implemented by "backing-off" the Class-A or Class-AB PA. However for a high peak-to-average (PAR) signal, the average efficiency is much lower than the peak efficiency, which is well down as the inherent trade-off between linearity and efficiency. This dissertation focuses on Envelope Elimination and Restoration (EER) and Envelope Tracking (ET) efficiency enhancement techniques to improve the PA average efficiency for high PAR signal. The EER and ET PA structures are investigated. Wideband ET and "hybrid" EER structures are proposed for WLAN 802.11g signal at 20MHz signal. Two major challenges of the wideband EER and ET PAs are investigated: 1) An adaptive time-alignment algorithm was proposed to calibrate the time-mismatch in wideband EER and ET systems; (2) A high efficiency wideband envelope amplifier is designed for wideband EER and wideband ET applications. A monolithic wideband high efficiency ET power amplifier is designed and implemented for WLAN 802.11g applications in IBM SiGe BiCMOS technology. Digital pre-distortion was implemented to reduce the EVM of the amplifier. The measured overall power-added efficiency of the amplifier is 28% at 20 dBm (100mW) output power. Mode of access: World Wide Web. Title from first page of PDF file (viewed January 4, 2007). Available via ProQuest Digital Dissertations. Thesis (Ph. D.)--University of California, San Diego, 2006. Vita. Includes bibliographical references (p. 126-131).
