Wideband Predistortion for Efficient Power Amplifiers

Abstract :

For three decades, the exchange rates in telecommunication standards have been exponentially increasing thanks to major innovations integrated from one generation to the following. The 5th generation of mobile standards 5G will, as its predecessors, provide a large increase of the data rates that will be made possible thanks to larger transmission bandwidths (up to several hundred of MHz) and to modulation schemes with higher spectral efficiency such as OFDMA and M-QAM. However, the novelty for 5G is the will to drastically minimize the power consumption with an objective of improving by 90% the energy efficiency compared to LTE standard. To achieve this objective, optimizations and innovations will be integrated at the different layers and levels of the communication systems. For the physical layer and more specifically both for the mixed signal and RF part, the power consumption should be also minimized. In the transceiver, the most power consuming component is the power amplifier (PA) and classically there is a trade-off between PA’s efficiency and its linear behavior. In order to relax the design constraints due to this trade-off and to improve linearity and power efficiency, predistortion has emerged as a go-to solution. A digital predistortion (DPD) system is conventionally composed of a digital predistorter in the transmission path in charge of applying the inverse non-linear (NL) transfer characteristic so that combined with the PA, the overall transfer characteristic is linear. The adjustment of the predistorter coefficients should be done continuously or regularly to compensate for process, voltage and temperature (PVT) variations of the PA and therefore requires an observation path. In 5G, the main challenges for the predistortion technique are the higher peak to average power ratio (PAPR) of the new modulation schemes and the large signal bandwidth which has grown to several hundred MHz. The combination of these two effects leads to higher constraints on : The compensation blocks (estimator + predistorter) because of the large growth of the number of coefficients required to properly linearize PAs that are expected to exhibit more nonlinearities and memory effects. The data converters (Digital to Analog Converter (DAC) + Analog to Digital Converter (ADC)) because they have to process a very wideband signal which is composed of the main signal plus the intermodulation products components. In this tutorial, a review is conducted of the main recent and promising solutions to implement efficient predistortion techniques for PA while maintaining affordable power consumption.

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https://hal.telecom-paristech.fr/hal-02288003
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Submitted on : Friday, September 13, 2019 - 5:34:58 PM
Last modification on : Tuesday, September 24, 2019 - 2:19:35 PM

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  • HAL Id : hal-02288003, version 1

Citation

Dang-Kièn Germain Pham, Patricia Desgreys. Wideband Predistortion for Efficient Power Amplifiers. International Conference on Electronics, Circuits and Systems (ICECS), Dec 2018, Bordeaux, France. ⟨hal-02288003⟩

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