Science Journal of Circuits, Systems and Signal Processing
Volume 3, Issue 3, June 2014, Pages: 14-25
Received: Oct. 12, 2014;
Accepted: Oct. 22, 2014;
Published: Oct. 30, 2014
Views 2654 Downloads 169
Walid Ahmed, Verizon Wireless, New Jersey, USA
Ajit Reddy, Alcatel-Lucent, New Jersey, USA
In this paper, a novel real-time closed-loop device linearization technique has presented. In this paper the focus application is on AM/AM and AM/PM linearization of power amplifiers (PA) and/or radio transmitters. In such an application, the novel approach performs on-the-fly measurement-and-prediction of the nonlinear characteristics of the PA, stores such non-linear characteristics and calculates their inverse functions in order to pre-distort the base-band amplitude and phase signals modulating the PA such that the combination, or the resultant, of the pre-distorter and the PA leads to a linear behavior at the output of the PA. The predictive nature of the presented approach overcomes the inevitable delay between the time a measurement is collected through the feedback loop and the time it has taken place at the output of the forward loop, which is a must-have delay encountered in any natural causal system. Such a delay results in imperfect on-the-fly pre-distortion of the output signal due to the mismatch between the applied pre-distortion, which has been based on a past measurement, and the actual effect of the non-linearity at the time the signal is produced . In addition, this novel approach promises the advantage of operating a highly non-linear (compressed) PA - hence, highly efficient - with minimal factory pre-calibration. We present a model of our predictor based approach and evaluate its performance for a GSM/EDGE/UMTS a cellular transmitter scenario, where the performance requirements on the transmitted signal are stringent and distortion due to non-linearity must be minimized. The key performance metrics we evaluate have mostly been based on the GSM/EDGE/UMTS requirements, such as the Error Vector Magnitude (EVM), Switching Transients (ST), and Adjacent Channel Power Ratio (ACPR), transmit time mask, modulation spectrum and power-added efficiency (PAE). Although the focus of the numerical results in this paper is on the GSM/EDGE/UMTS application, the novel approach discussed is applicable to any TDMA or TDD system where switching transients and spectral performance is tightly controlled.
Novel Real-Time Closed-Loop Device Linearization via Predictive Pre-Distortion, Science Journal of Circuits, Systems and Signal Processing.
Vol. 3, No. 3,
2014, pp. 14-25.
Walid K. M. Ahmed and Qing Li, “Method and Apparatus for a Nonlinear Feedback Control System”. U.S. Patent# 7,889,810.
3GPP TS 45.005 V7.8.0. Digital Cellular Telecommunications Systems; Radio transmission and reception (Release 2006-11).
3GPP TS 51.021 V7.1.0. Base Station System (BSS) equipment specification; Radio aspects (Release 2005-11).
Walid Ahmed, “Methods and Apparatus for Signal Power Ramp-up in a Communication System”, U.S. Patent Application No. 11/385212.
M. Nezami, “Fundamentals of Power Amplifier Linearization Using Digital Pre-Distortion”, High Frequency Electronics, September 2004, pp. 54-59.
W. Ahmed and D. Douglas, “Multi-mode selectable modulation architecture calibration and power control apparatus, system, and method for radio frequency power amplifier”. U.S. Patent# 7,599,448.
SCHETZEN M.: ‘The Volterra and Wiener theories of nonlinear systems’ (Krieger Publishing Co., 2006).
P. Nagle, R. Husseini, A. Grebennikov, W. K. M. Ahmed and F. McGrath, “A novel wideband digital power amplifier and transmitter architecture for multimode handsets”, In Proc. Of the 2004 IEEE Radio and Wireless Conference, pp. 171 - 174.
Walid K. M. Ahmed, “Quantization Noise Suppression in Digitally Segmented Amplifiers”, IEEE Transactions on Circuits and Systems I: Regular Papers, Volume 56, Issue 3, March 2009, pp. 529 - 540.
P. L. Gilabert, A. Cesari, G. Montoro, E. Bertran, and J.-M. Dilhac, “Multi-lookup table FPGA implementation of an adaptive digital predistorter for linearizing RF power amplifiers with memory effects,” IEEE Trans. Microw. Theory Tech., vol. 56, no. 2, pp. 372–384, Feb. 2008.
A. Zhu, P. J. Draxler, J. J. Yan, T. J. Brazil, D. F. Kimball, P. M. Asbeck, “ Open-Loop Digital Predistorter for RF Power Amplifiers Using Dynamic Deviation Reduction-Based Volterra Series,” IEEE Trans. Microw. Theory Tech., vol. 56, no. 7, pp. 1524-1534, July 2008.
S.Saied-Bouajina, O. Hammi, M.Jaidane-Saidane and F.M. Ghannouchi, “Experimental approach for robust identification of radiofrequency power amplifier amplifier behavior models using polynomial structures”, IET Microwave Antennas Propogation, 2010, vol. 4, issue 11, pp. 1818-1828.
Ding L., Zhou G.T., Morgan D.R., et al. ‘A robust digital baseband predistorter constructed using memory polynomials’, IEEE Trans. Commun., 2004, 52, (1), pp. 159–165.
Kim J., Konstantinou K.: ‘Digital predistortion of wideband signals based on power amplifier model with memory’, Electron. Lett., 2001, 37, (23), pp. 1417–1418.
Jeckeln E.G., Beauregard F., Sawan M.A., Ghannouchi F.M.‘Adaptive baseband/RF predistorter for power amplifiers through instantaneous AM-AM and AM-PM characterization using digital receivers’. Dieg. 2000 IEEE MTT-S Int. Microwave Symp., Boston, MA, USA, June 2000, pp. 489–492.