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Yan Li, Ranko Sredojevic, Zhipeng Li, Oguzhan Uyar, Prof. Vladimir Stojanovic in collaboration with Prof. Megretski's research group and Prof. Dawson's research group at MIT and Prof. Rickets' research group at CMU

Compensation Architectures for Asymmetrical Multi-level Outphasing Amplifier

Recent advances in silicon technology and wireless standards have promoted developments of multi-Gb/s wireless communication systems at RF/mm-wave regime (eg. 60GHz and beyond). This gives a great challenge to the power amplifier (PA) design, where the trade-off between linearity and power efficiency becomes more severe as the bandwidth and carrier frequency increase. In this project, we plan to tackle the problem from several perspectives.

An asymmetrical multi-level outphasing (AMO) architecture has been proposed recently [1] and showed its promises in improving efficiency and linearity of power amplifier simultaneously. We design an energy-efficient VLSI implementation of the digital back-end for the AMO, and integrating this digital back-end with PA part seamlessly.

Figure 1: An asymmetrical multi-level outphasing architecture [1]

Though there are many commonly used system identification techniques (e.g. Wiener-Hamerstein structure), among which [2] shows a nice identification method with incremental stability ensured, the challenge here still remains. The specific nonlinearities of this new PA structure arise from power supply ringing, path delay mismatch, and thermal effects, and possibly other sources. Specifically, we are exploring these sources of nonlinearities and are trying to work out a identification/compensation technique which 1) favors an energy-efficient digital implementation, 2) is aware of the additional specification on spectral mask, in addition to the traditional goal of small EVM.

References

1. SungWon Chung, Philip A. Godoy, Taylor W. Barton, Everest W. Huangy, David J. Perreault, and Joel L. Dawson, “Asymmetric Multilevel Outphasing Architecture for Multi-standard Transmitters”, RFIC, 2009
2. Bradley N. Bond, Zohaib Mahmood, Yan Li, Ranko Sredojevi´c, Alexandre Megretski, Vladimir Stojanovi´c, Yehuda Avniel, Luca Daniel, “Compact Modeling of Nonlinear Analog Circuits using System Identification via Semidefinite Programming and Incremental Stability Certification”, TCAD, 2010.