| Summary: | 碩士 === 國立中央大學 === 電機工程研究所 === 97 === Power amplifier is a very important component in the wireless transmitter. The high performance power amplifier must depend on accurate nonlinear device model. In this thesis, an accurate nonlinear model and a high linearity power amplifier are designed, analyzed, and demonstrated for InGaAs pHEMT.
We proposed a novel current model for 0.5 μm InGaAs pHEMTs enhancement-mode device. The model is differentiable for any order at full bias range by utilizing smooth function technique in the symbolical defined device environment (SDD). The Statz charge model is included for device capacitance in this model. The proposed model predicted the DC, S-parameters, microwave power, and nonlinear distortion characteristics more accurate in comparison with conventional compact model. Further, the model is convenient and direct to be embedded in commercial harmonic balanced simulator.
Utilizing nonlinear model tools, the high performance power amplifier was realized for WiMAX applications. The predistortion method in this work was used to improve AM-AM and AM-PM distortion at high power operation without degrading the intrinsic performance. The power amplifier was successfully demonstrated at 3.5 GHz. The power performances were power gain of 16 dB, maximum power of 29.5 dBm, output linear power (P1dB) of 27.5 dBm. The measured EVM was smaller than 3.5 % using 3.5 GHz 64 QAM WiMAX signal.
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