A Single Envelope Modulator-Based Envelope-Tracking Structure for Multiple-Input and Multiple-Output Wireless Transmitters

A single envelope modulator-based envelope tracking (ET) power amplifier (PA) structure with a related digital predistortion (DPD) technique for multiple-input and multiple-output (MIMO) wireless transmitters is presented in this paper. By generating a common tracking envelope, only one envelope modulator is employed for controlling supply voltage of the RF PAs in all branches in the system, which dramatically reduces the system implementation cost. Due to the structure change, additional distortion is introduced, and it is difficult to directly compensate by using the conventional DPD because the tracking envelope is no longer the same as the RF envelope, and thus the MIMO ET PA becomes a two-input and one-output system. To resolve this problem, in this paper we propose a novel DPD technique in which the PA input and output data are reconstructed into multiple data subsets according to variations of the tracking envelope. It converts the 2-to-1 mapping into multiple 1-to-1 ones, where the conventional DPD can be employed again. Experimental results demonstrated that the distortion, including static nonlinearities, memory effects, and additional distortion caused by the structure change can be effectively compensated by using the proposed DPD technique. Compared to the conventional ET, the overall efficiency of the system is only slightly decreased, but the system cost is much lower because only one envelope modulator is required in the whole system.

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

[2]  Pere L. Gilabert,et al.  Digital Predistortion of Envelope Tracking Amplifiers driven by slew-rate limited envelopes , 2011, 2011 IEEE MTT-S International Microwave Symposium.

[3]  P. Asbeck,et al.  High-Efficiency Envelope-Tracking W-CDMA Base-Station Amplifier Using GaN HFETs , 2006, IEEE Transactions on Microwave Theory and Techniques.

[4]  V. J. Mathews,et al.  Polynomial Signal Processing , 2000 .

[5]  Anding Zhu,et al.  Digital Predistortion for Envelope-Tracking Power Amplifiers Using Decomposed Piecewise Volterra Series , 2008, IEEE Transactions on Microwave Theory and Techniques.

[6]  Robert H. Caverly,et al.  HF, VHF, and UHF systems and technology , 2002 .

[7]  Lei Guan,et al.  Optimized Low-Complexity Implementation of Least Squares Based Model Extraction for Digital Predistortion of RF Power Amplifiers , 2012, IEEE Transactions on Microwave Theory and Techniques.

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

[9]  Jonmei J. Yan,et al.  Open-Loop Digital Predistorter for RF Power Amplifiers Using Dynamic Deviation Reduction-Based Volterra Series , 2008, IEEE Transactions on Microwave Theory and Techniques.

[10]  S. C. Cripps,et al.  RF Power Amplifiers for Wireless Communications , 1999 .

[11]  Zhenghe Feng,et al.  Linearization of Concurrent Dual-Band Power Amplifier Based on 2D-DPD Technique , 2011, IEEE Microwave and Wireless Components Letters.

[12]  Feipeng Wang,et al.  A Monolithic High-Efficiency 2.4-GHz 20-dBm SiGe BiCMOS Envelope-Tracking OFDM Power Amplifier , 2007, IEEE Journal of Solid-State Circuits.

[13]  C. Fager,et al.  Digital Predistortion for High Efficiency Power Amplifier Architectures Using a Dual-Input Modeling Approach , 2012, IEEE Transactions on Microwave Theory and Techniques.

[14]  Edward J. Powers,et al.  A new Volterra predistorter based on the indirect learning architecture , 1997, IEEE Trans. Signal Process..

[15]  Taijun Liu,et al.  Pre-compensation for the dynamic nonlinearity of wideband wireless transmitters using augmented Wiener predistorters , 2005, 2005 Asia-Pacific Microwave Conference Proceedings.

[16]  G. Montoro,et al.  A New Digital Predictive Predistorter for Behavioral Power Amplifier Linearization , 2007, IEEE Microwave and Wireless Components Letters.

[17]  F. Raab,et al.  Power amplifiers and transmitters for RF and microwave , 2002 .

[18]  P. Draxler,et al.  Wideband Envelope Tracking Power Amplifiers With Reduced Bandwidth Power Supply Waveforms and Adaptive Digital Predistortion Techniques , 2009, IEEE Transactions on Microwave Theory and Techniques.

[19]  T.J. Brazil,et al.  An adaptive Volterra predistorter for the linearization of RF high power amplifiers , 2002, 2002 IEEE MTT-S International Microwave Symposium Digest (Cat. No.02CH37278).

[20]  Dennis R. Morgan,et al.  A robust digital baseband predistorter constructed using memory polynomials , 2004, IEEE Transactions on Communications.

[21]  A. Cid-Pastor,et al.  A DSP structure authorizing reduced-bandwidth DC/DC Converters for Dynamic Supply of RF Power Amplifiers in Wideband Applications , 2006, IECON 2006 - 32nd Annual Conference on IEEE Industrial Electronics.

[22]  G. Montoro,et al.  Look-Up Table Implementation of a Slow Envelope Dependent Digital Predistorter for Envelope Tracking Power Amplifiers , 2012, IEEE Microwave and Wireless Components Letters.

[23]  L.E. Larson,et al.  Design of wide-bandwidth envelope-tracking power amplifiers for OFDM applications , 2005, IEEE Transactions on Microwave Theory and Techniques.