Session: WE3F

1:20 PM Wednesday, May 26, 2010

Room: 208AB
     
Session: WE3F
Techniques to Enhance Power Amplifier Linearity and Efficiency
Chair:
Wayne Kennan, ACCO Semiconductor, Inc
Co-Chair:
Raghu Mallavarpu, Raytheon Company
Abstract:
The papers in this session discuss a variety of techniques to simultaneously achieve high linearity and efficiency. The techniques described are based on Doherty, tunable output matching, adaptive digital pre-distortion, pulse modulation, and Class S operation.
 
 
WE3F-1
30.3% PAE HBT Doherty Power Amplifier for 2.5~2.7 GHz Mobile WiMAX
1:20 PM-1:40 PM
D. Kang1, J. Choi1, D. Kim1, D. Yu2, K. Min2, B. Kim1, 1Postech, Pohang, Republic of Korea, 2WiPAM, Seongnam, Republic of Korea
(1387)
The Doherty power amplifier for mobile WiMAX application is fully integrated in 1.2 mm x 1.2 mm using a 2-um InGaP/GaAs HBT process. The direct input power dividing technique is employed on a chip. Broadband input and output matching techniques are used for broadband Doherty operation. A 1.5 times larger peaking amplifier than carrier amplifier is used to have high efficiency for IEEE 802.16e m-WiMAX signal, which has 9.6 dB crest factor and 8.75 MHz bandwidth. The PA with a supply voltage of 3.4V has an EVM of 2.3% and a PAE of 31.5% at an output power of 24.75 dBm and an operating frequency of 2.6 GHz. The PAE of over 30.3% and the output power of over 24.6 dBm with the EVM of lower than 3.15% and the gain variation of 0.2 dB are achieved across 2.5~2.7 GHz without any assistant technique for linearization.
 
 
WE3F-2
A Fully Integrated CMOS RF Power Amplifier with Tunable Matching Network for GSM/EDGE Dual-Mode Application
1:40 PM-2:00 PM
H. Kim1, Y. Yoon1, O. Lee1, K. An1, D. Lee2, W. Kim3, C. Lee3, J. Laskar1, 1Georgia Electronic Design Center, Georgia Institute of Technology, Atlanta, United States, 2Skyworks, Cedar Rapids, United States, 3Samsung Design Center, Atlanta, United States
(1838)
A fully integrated power amplifier operating at switching and linear mode is implemented using 0.18-um CMOS technology. To maximize performance for both operation modes, the fundamental load impedances are optimized with a variable capacitor for GSM and EDGE application. For GSM application, 32 dBm of the output power with 45 % of the drain efficiency is achieved at 1.76 GHz. With EDGE modulation signal at 1.76 GHz, error vector magnitude (EVM) has an RMS value of less than 5 % up to 27.5 dBm of the output power, and 28.1 % of modulated PAE is achieved at this power. The output spectrum is confined within the inside of mask up to 27.5 dBm of the output power.
 
 
WE3F-3
Efficiency Improvement of a Handset WCDMA PA Module Using Adaptive Digital Predistortion
2:00 PM-2:20 PM
C. D. Presti1, A. G. Metzger2, H. M. Banbrook2, P. J. Zampardi2, P. M. Asbeck1, 1University of California, San Diego, La Jolla, United States, 2Skyworks Solutions Inc., Newbury Park, United States
(1712)
Adaptive Digital Predistortion (DPD) is applied to a spec-compliant class-AB GaAs HBT PA module for WCDMA handsets. It is shown that, by using a re-optimized load line, the efficiency can be increased from 37.5% to 47% at nominal 28.5 dBm output power, while maintaining the same excellent linearity of the original PA. The quiescent current consumption is also reduced down to 40 mA at all power levels, enabling up to 49% average dc power savings without dynamic biasing. Under 2:1 VSWR, 7% to 11% higher PAE is demonstrated at 28 dBm, achieving significant ACPR reduction as well. The methodology to tradeoff the linearization capability of DPD to optimize efficiency at a specified power and linearity is discussed in detail.
 
 
WE3F-4
A Pulse Modulated Polar Transmitter for CDMA Handsets
2:20 PM-2:40 PM
H. Yang1, H. Shih1, J. Chen2, Y. E. Chen1, 1National Taiwan University, Taipei, Taiwan, 2National Taiwan University, Taipei, Taiwan
(1270)
This paper presents a pulse modulated polar transmitter with the designed class-E power amplifiers for CDMA handsets. Compared to the conventional drain/collector-modulated envelope elimination and restoration transmitter, the presented implementation is capable of reducing circuit complexity and making the envelope and RF phase signals easily synchronized. A prototype transmitter system is constructed using commercially available components. Measuring using a CDMA IS-95 signal at 900 MHz, it achieves 49.3% efficiency at 26.6-dBm output power level while passing the adjacent and alternate channel power ratio requirements without using any pre-distortion or calibration. Moreover, the polar transmitter achieves more than 20 dB of output dynamic range.
 
 
WE3F-5
RF Class-S Power Amplifiers: State-of-the-Art Results and Potential
2:40 PM-3:00 PM
A. Wentzel, C. Meliani, W. Heinrich, Ferdinand-Braun-Institut (FBH), Leibniz-Institut fuer Hoechstfrequenztechnik, Berlin, Germany
(1206)
This paper reports recent results on a current-mode class-S power amplifier for the 450 MHz band, based on GaN-HEMT MMICs. We achieve a peak output power of 8.7 W for a single tone at 420 MHz, encoded in standard band-pass delta-sigma modulation with 1.68 Gbps sampling frequency. The respective efficiency is 34%. We find that these values strongly vary with coding efficiency of the modulation and reach 19 W with 59% for square-wave excitation. In order to clarify the potential of the PA in more detail, the S-class characteristics at power back-off and with varying oversampling ratio are presented as well.
 
 
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