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Signal Processing and Speech Communication Laboratory 1 A Joint Linearity-Efficiency Model of Radio Frequency Power Amplifiers Harald Enzinger, Karl Freiberger, Christian Vogel IEEE International Symposium on Circuits and Systems Montreal, Canada 23.05.2016 u www.spsc.tugraz.at 2 Motivation Behavioral Model of Linearity and Efficiency Based on measurements Based on theoretical model subject of this work IEEE International Symposium on Circuits and Systems 23.05.2016 3 Power Amplifier Circuit Model Chapter Headline IEEE International Symposium on Circuits and Systems 23.05.2016 4 Waveform of Drain Current Conduction Angle Saturation Angle Quiescent Point Input Amplitude normalized to fullscale IEEE International Symposium on Circuits and Systems 23.05.2016 5 Fourier Series of Drain Current Linear Model IEEE International Symposium on Circuits and Systems 23.05.2016 Cubic Model 6 Harmonics of Drain Current Linear Model Class AB Class A Cubic Model Class C Class B IEEE International Symposium on Circuits and Systems 23.05.2016 Class AB Class A Class C Class B 7 From Current to Power Assumptions Ideal output matching Match at first harmonic Short at higher harmonics Ideal transistor output Zero knee voltage Zero output conductance IEEE International Symposium on Circuits and Systems 23.05.2016 8 Linearity and Efficiency AM-AM Characteristic Instantaneous Efficiency IEEE International Symposium on Circuits and Systems 23.05.2016 9 Average Efficiency Definition Time-Domain Ensemble-Domain IEEE International Symposium on Circuits and Systems 23.05.2016 10 Application Example Setup Class AB model Various signals With / without DPD Observations Average efficiency is mainly defined by required backoff With DPD, the backoff can be reduced IEEE International Symposium on Circuits and Systems 23.05.2016 11 Matlab Code http://www.mathworks.com/matlabcentral/fileexchange/53413 calcPaModel PA-Model, consisting of 2 memoryless lookup-tables calcPaSignal demo_calcPaModel Demo-Script for calculation of PA characteristics demo_calcPaSignal Demo-Script for simulation of input-output behavior IEEE International Symposium on Circuits and Systems 23.05.2016 12 Conclusion Theoretical Model of Linearity and Efficiency Includes strong nonlinearity due to current clipping Includes weak nonlinearity due to transconductance variation Does not include nonlinear memory effects Potential Applications High-level system simulations Study of new transmitter architectures Education IEEE International Symposium on Circuits and Systems 23.05.2016