A broadband SiGe power amplifier in an efficient polar transmitter using envelope-tracking for mobile WiMAX (original) (raw)
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IEEE Transactions on Circuits and Systems I-regular Papers, 2011
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 m SiGe BiCMOS technology, and a linear-assisted switch-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%.
2009
A decresting algorithm for mobile WiMAX has been developed using time domain clipping and filtering processes for a polar transmitter (TX) using Envelope-Tracking (ET) and a monolithic SiGe power amplifier (PA). RF/Analog/Digital system and circuits co-design simulations have been performed for mobile WiMAX with 64 QAM OFDM modulation format. It is found that higher power-to-average ratio (PAR) decresting can improve the adjacent channel power ratio (ACPR) and the overall TX system efficiency, but at the cost of its EVM degradation. Our system simulations show that careful design of signal decresting can improve the overall polar TX system efficiency from 28.1% to 30.3% while the TX output can still meet the stringent WiMAX TX mask and EVM specs.
2010
This paper presents a highly-efficient polar transmitter (TX) system that adopts the envelopetacking (ET) technique with a differential SiGe power amplifier (PA) for 3GPP Long Term Evolution (LTE) applications. The differential PA was designed using a cascode topology, reaching power-added efficiency (PAE) of 50% at output power of 22dBm in continuous wave (CW) mode. The experimental data also shows that the proposed ET-based polar TX system with the cascode PA delivers 21dBm average output power with 33.6% PAE at 1.42 GHz, while also meeting the LTE 16QAM linearity specs for both error vector magnitude (EVM) and TX emission mask without the need of PA predistortion.
IEEE Transactions on Microwave Theory and Techniques, 2011
This paper presents a SiGe envelope-tracking (ET) cascode power amplifier (PA) with an integrated CMOS envelope modulator for mobile WiMAX and 3GPP long-term evolution (LTE) transmitters (TXs). The entire ET-based RF PA system delivers the linear output power of 22.3/24.3 dBm with the overall power-added efficiency of 33%/42% at 2.4 GHz for the WiMAX 64 quadrature amplitude modulation (64QAM) and the 3GPP LTE 16 quadrature amplitude modulation, respectively. Additionally, it exhibits a highly efficient broadband characteristic for multiband applications. Compared to the conventional fixed-supply cascode PA, our ET-based cascode PA meets the WiMAX/LTE spectral mask and error vector magnitude spec at close to its 1dB compression without the need of predistortion. The SiGe PA and the CMOS envelope modulator are both designed and fabricated in the TSMC 0.35m SiGe BiCMOS process on the same die. This study represents an essential integration step toward achieving a fully monolithic large-signal ET-based TX for wideband wireless applications.
SiGe class-E power amplifier with envelope tracking for mobile WiMAX/Wibro applications
2009
In this paper, we report both circuits design and system simulations using highly-efficient monolithic SiGe class-E power amplifier (PA) with an open-loop envelope tracking (ET) technique for mobile WiMAX/Wibro applications. The 1-stage and 2-stage class-E PAs were designed and fabricated in a 0.18 mum BiCMOS SiGe technology. The 1-stage class-E PA achieved peak power added efficiency (PAE) of 62% at output power of 21 dBm in single-tone measurement. The design of linear-assisted switching envelope amplifier is also discussed, which involves balancing the tradeoff between efficiency and signal fidelity. Detailed co-design system simulations including RF circuits and digital DSP blocks show that our class-E PA can be linearized by the open-loop ET technique, and the entire ET-based transmit (TX) system meets the stringent 802.16e TX mask with ~33% overall average efficiency at output power of 18.5 dBm.
A high efficiency SiGe BiCMOS envelope-tracking power amplifier for W-CDMA applications
2013 Texas Symposium on Wireless and Microwave Circuits and Systems (WMCS), 2013
This paper presents a highly efficient power amplifier (PA) using the envelope tracking (ET) technique for 3G W-CDMA applications. The PA is designed in the IBM 0.35-m SiGe BiCMOS process with through-silicon-via (TSV). The CMOS envelope modulator IC is designed and fabricated in the TSMC 0.35-m SiGe BiCMOS process. The ET-PA system achieves an overall composite power-addedefficiency (PAE) of 35.4% at P OUT of 26.5 dBm at 900 MHz with the W-CDMA signal and improves the PAE by 5% compared to that of the fixed-supply standalone SiGe PA.
A Linear Assisted Switching Envelope Amplifier for a UHF Polar Transmitter
IEEE Transactions on Power Electronics, 2014
Spectrally efficient wireless communication standards impose stringent linearity specifications, which would require traditional IQ transmitters to operate with back-offed and power inefficient linear RF power amplifiers (PAs). In order to overcome such a significant limitation, alternative architectures have been proposed, as those based on the Envelope Elimination and Restoration (EER) technique. An example of the application of this technique is the Polar Transmitter. In this paper, a UHF Polar Transmitter is presented, combining switching and linear stages in the envelope amplifier as to achieve both wide bandwidth and high efficiency, when drain modulating a GaN HEMT Class E RF PA. Several tests, using EDGE, TETRA, and WCDMA standards have been performed with good results.
A Monolithic High-Efficiency 2.4GHz 20dBm SiGe BiCMOS Envelope-Tracking OFDM Power Amplifier
IEEE Journal of Solid-state Circuits, 2007
A monolithic SiGe BiCMOS envelope-tracking power amplifier (PA) is demonstrated for 802.11g OFDM applications at 2.4 GHz. The 4-mm 2 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%.
2009 IEEE MTT-S International Microwave Symposium Digest, 2009
We have demonstrated a highly efficient Hybrid Envelope Elimination and Restoration transmitter for IEEE 802.16e Mobile WiMAX application using a highly efficient saturated Power amplifier (PA). For the optimum H-EER operation, the PA has been designed to have a maximum PAE at the average Vds region by using 10 W (P 3dB ) GaN High Electron Mobility Transistor. The maximum Power-added efficiency (PAE) is a 74.07 % at the 14 V Vds. The bias modulator designed using a Hybrid Switching Amplifier (HSA) has a 73.3 % of efficiency. In the interlock experiment, the transmitter has shown an excellent PAE performance of 45.9 % at an average output power of 33.07 dBm with drain efficiency (DE) of 48.86 %. By using digital predistortion technique, the Relative Constellation Error (RCE) has been satisfied the specification of -30 dB with -36.88 dB. When considering the saturated PA with constant drain bias, the average PAE of the proposed transmitter has been hugely improved, about 13.64 %. These results clearly show that the H-EER transmitter using the saturated PA can deliver the excellent PAE performance.
IEEE Transactions on Circuits and Systems I-regular Papers, 2015
We present a highly efficient RF transmitter over broad average power range using a multilevel envelope-tracking power amplifier (ML-ET PA). The ML-ET PA delivers enhanced efficiency at a back-off power region for handset applications. The supply modulator consists of a linear regulator and a switching converter. The DC supply of the linear regulator is adjusted according to the average power of the envelope signal, and the power-supply-independent class-AB output stage is employed to avoid the crossover distortion generated by the different DC supply voltages. The switch current level is not optimally adjusted by itself following the power back-off level, because the DC supply voltages of the linear regulator and switching converter are different. For the optimum operation over the entire power region, the switch current level is adjusted by detecting the input envelope voltage level. For a 20-MHz long term evolution signal with a 7.5 dB peak-to-average power ratio, the proposed supply modulator delivers a peak voltage of 4.5 V to a 6.5 load with a measured efficiency of 75.9%. The proposed ET PA delivers a power-added efficiency (PAE) of 40%, gain of 28.8 dB, evolved universal terrestrial radio access adjacent channel leakage ratio of 35.3 dBc, and error vector magnitude of 3.23% at an average output power of 27 dBm and an operating frequency of 1.71-GHz. At a 10 dB back-off point, the PAE is improved from 14.5% to 18.7% compared to the conventional ET PA.