Linearization and Imbalance Correction Techniques for Broadband Outphasing Power Amplifiers

This paper presents adaptive phase-only memory digital pre-distortion (DPD) and gain/phase/delay imbalance correction techniques for outphasing power amplifiers (PAs). Least squares adaptation is used for the phase-only DPD and imbalance correction techniques. The performance of these techniques is verified by co-simulations and measurements of an outphasing PA implemented with two identical class-F PAs and a Chireix combiner. The Chireix combiner with compensating stubs added to achieve high efficiency introduces nonlinearity. The proposed adaptive phase-only memory DPD corrects for the nonlinearity due to the Chireix combiner. The proposed gain/phase/delay imbalance correction technique achieves total lower/upper adjacent channel power ratio (ACPR) improvements of 43.8/37.6 dB for 5-MHz and 46.2/38.3 dB for 10-MHz long-term-evolution signals in measurements. The fractional-sample delay imbalance correction reduces distortion at low input amplitudes and demonstrates on the order of a 10-dB ACPR improvement compared to full-sample delay imbalance correction.

[1]  Mark P. van der Heijden,et al.  A 19W high-efficiency wide-band CMOS-GaN class-E Chireix RF outphasing power amplifier , 2011, 2011 IEEE MTT-S International Microwave Symposium.

[2]  Jacob Benesty,et al.  Time-delay estimation via linear interpolation and cross correlation , 2004, IEEE Transactions on Speech and Audio Processing.

[3]  Lawrence E. Larson,et al.  Gain and phase error-free LINC transmitter , 2000, IEEE Trans. Veh. Technol..

[4]  Fadhel M. Ghannouchi,et al.  Thermal memory effects modeling and compensation in RF power amplifiers and predistortion linearizers , 2003 .

[5]  Jangheon Kim,et al.  Power Efficiency and Linearity Enhancement Using Optimized Asymmetrical Doherty Power Amplifiers , 2011, IEEE Transactions on Microwave Theory and Techniques.

[6]  Atila Alvandpour,et al.  Least-Squares Phase Predistortion of a +30 dBm Class-D Outphasing RF PA in 65 nm CMOS , 2013, IEEE Transactions on Circuits and Systems I: Regular Papers.

[7]  Lars Sundström.  Automatic adjustment of gain and phase imbalances in LINC transmitters , 1995 .

[8]  Fernando Casadevall,et al.  On the behavior of the LINC transmitter , 1990, 40th IEEE Conference on Vehicular Technology.

[9]  C. Weitzel,et al.  RF power amplifiers for wireless communications , 2002, 24th Annual Technical Digest Gallium Arsenide Integrated Circuit (GaAs IC) Symposiu.

[10]  S. A. Olson,et al.  LINC imbalance correction using baseband preconditioning , 1999, RAWCON 99. 1999 IEEE Radio and Wireless Conference (Cat. No.99EX292).

[11]  Atila Alvandpour,et al.  Phase Predistortion of a Class-D Outphasing RF Amplifier in 90 nm CMOS , 2011, IEEE Transactions on Circuits and Systems II: Express Briefs.

[12]  Olivier Venard,et al.  Gain and delay mismatches cancellation in LINC and polar transmitters , 2010, Proceedings of 2010 IEEE International Symposium on Circuits and Systems.

[13]  M. Marchetti,et al.  A 90-W Peak Power GaN Outphasing Amplifier With Optimum Input Signal Conditioning , 2009, IEEE Transactions on Microwave Theory and Techniques.

[14]  Jaehyeong Kim,et al.  A Generalized Memory Polynomial Model for Digital Predistortion of RF Power Amplifiers , 2006, IEEE Transactions on Signal Processing.

[15]  Unto K. Laine,et al.  Splitting the unit delay [FIR/all pass filters design] , 1996, IEEE Signal Process. Mag..

[16]  Hamed S. Al-Raweshidy,et al.  Gain/phase imbalance cancellation technique in LINC transmitters , 1998 .

[17]  Rajeev Gandhi,et al.  Adaptive algorithms for calibrating a LINC amplifier , 2001, Proceedings RAWCON 2001. 2001 IEEE Radio and Wireless Conference (Cat.No.01EX514).

[18]  Antonio Valdovinos,et al.  An adaptive digital method of imbalances cancellation in LINC transmitters , 2005, IEEE Transactions on Vehicular Technology.

[19]  J. Stevenson Kenney,et al.  Predicting spectral regrowth of nonlinear power amplifiers , 2002, IEEE Trans. Commun..

[20]  Jungsang Kim,et al.  Digital predistortion of wideband signals based on power amplifier model with memory , 2001 .

[21]  Mark A Beach,et al.  Combining envelope elimination and restoration and predistortion techniques for use in IEEE802.11g systems , 2007 .

[22]  Kamran Azadet,et al.  Class-F power amplifier with 80.1% maximum PAE at 2 GHz for cellular base-station applications , 2013, WAMICON 2013.

[23]  Zoya Popovic,et al.  Tunable outphasing for power amplifier efficiency improvement under load mismatch , 2012, 2012 IEEE/MTT-S International Microwave Symposium Digest.

[24]  A. Kouki,et al.  Phase-only predistortion for LINC amplifiers with Chireix-outphasing combiners , 2005, IEEE Transactions on Microwave Theory and Techniques.

[25]  Mustafa Acar,et al.  A Package-Integrated Chireix Outphasing RF Switch-Mode High-Power Amplifier , 2013, IEEE Transactions on Microwave Theory and Techniques.

[26]  Ockgoo Lee,et al.  An Amplitude and Phase Mismatches Calibration Technique for the LINC Transmitter With Unbalanced Phase Control , 2011, IEEE Transactions on Vehicular Technology.

[27]  C.P. Silva,et al.  Validation of power amplifier nonlinear block models , 1999, 1999 IEEE MTT-S International Microwave Symposium Digest (Cat. No.99CH36282).

[28]  Renato Negra,et al.  Linearity study of path imbalances in multi-level LINC transmitter for wideband LTE application , 2013, 2013 European Microwave Conference.

[29]  William R. Panton,et al.  Effects of nonlinear distortion on CDMA communication systems , 1996, IMS 1996.

[30]  Kamran Azadet,et al.  Characterization of Class-F Power Amplifier With Wide Amplitude and Phase Bandwidth for Outphasing Architecture , 2014, IEEE Microwave and Wireless Components Letters.

[31]  A. Alvandpour,et al.  Modeling and Digital Predistortion of Class-D Outphasing RF Power Amplifiers , 2012, IEEE Transactions on Microwave Theory and Techniques.

[32]  H. Chireix.  High Power Outphasing Modulation , 1935, Proceedings of the Institute of Radio Engineers.

[33]  David Hertz,et al.  Time delay estimation by combining efficient algorithms and generalized cross-correlation methods , 1986, IEEE Trans. Acoust. Speech Signal Process..