Optimal spacing for a polar look-up table predistorter

Modern modulation standards utilize undistorted complex non-constant envelope modulation schemes for improved spectral efficiency and transmit data bandwidth. On the contrary, the increased demand of power added efficiency for longer battery life forces the power amplifiers to be operated well into their non-linear operational region. The transmitter and PA non- linearities, if uncompensated, result in many undesired effects such as spectral regrowth and degradation of BER. Look-up-table (LUT) based predistorters have been widely used to mitigate the effects of nonlinear PA's. LUT refinements techniques such as optimal spacing have been studied for zero-hold LUT (ZOH- LUT) in the complex gain predistorter configuration. In this paper, optimal spacing for the polar LUT predistorter is studied. An optimal spacing is derived for both ZOH-LUT and Linearly interpolated LUT (Lin-LUT). An analytical study of Lin-LUT shows that the mean squared approximation error is decreased by 12 dB when the LUT size is doubled, as opposed to 6 dB for ZOH interpolation.

[1]  Michael Faulkner,et al.  Adaptive linearization using predistortion-experimental results , 1994 .

[2]  James K. Cavers,et al.  Amplifier linearization using a digital predistorter with fast adaptation and low memory requirements , 1990 .

[3]  M. Kamarei,et al.  A flexible method of LUT indexing in digital predistortion linearization of RF power amplifiers , 2001, ISCAS 2001. The 2001 IEEE International Symposium on Circuits and Systems (Cat. No.01CH37196).

[4]  K. Halonen,et al.  Baseband Digital Predistorter with Quadrature Error Correction , 2004, Proceedings Norchip Conference, 2004..

[5]  James K. Cavers.  Optimum table spacing in predistorting amplifier linearizers , 1999 .

[6]  Michael Faulkner,et al.  Quantization analysis and design of a digital predistortion linearizer for RF power amplifiers , 1996 .

[7]  Jiunn-Tsair Chen,et al.  Dynamically optimum lookup-table spacing for power amplifier predistortion linearization , 2006 .

[8]  M. Jaidane-Saidane,et al.  Adaptive digital/RF predistortion using a nonuniform LUT indexing function with built-in dependence on the amplifier nonlinearity , 2004, IEEE Transactions on Microwave Theory and Techniques.

[9]  Chen Kang-shen,et al.  Adaptive predistortion for RF power amplifier based on new look-up table indexing method , 2002, 2002 3rd International Conference on Microwave and Millimeter Wave Technology, 2002. Proceedings. ICMMT 2002..

[10]  Mohsen Kavehrad,et al.  Look-up table techniques for adaptive digital predistortion: a development and comparison , 2000, IEEE Trans. Veh. Technol..

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

[12]  Allen Gersho,et al.  Principles of quantization , 1978 .

[13]  K. Waheed,et al.  Adaptive digital linearization of a DRP based edge transmitter for cellular handsets , 2007, 2007 50th Midwest Symposium on Circuits and Systems.