Power Efficient Amplifier Model Considering Drain Current Dependence upon Input Power for Mobile Communication Applications

摘要

Simple and accurate transfer equations of power amplifier for mobile communications that requires linearity compensation technique such as predistortion due to its severe nonlinear AM/AM and AM/PM characteristics are studied. This paper proposes AM/AM characteristics model of AB, B, and C class high efficient power amplifiers employing PHEMT by consideration of drain current variation according to input level. Generalized model is shown as relation of input voltage amplitude V{sub}i and output voltage V{sub}0 by load line variation ratio k introducing to indicate the change of drain current and the value at no input signal represents operation classes. And further discussion derives simple approximate equations from the generalized model. Finally, comparison between the results obtained by the model, simulator, and measurement shows that they are very close at the range of 20 dB below saturation output power of amplifiers.