| Summary: | 碩士 === 國立中正大學 === 電機工程研究所 === 105 === This thesis includes two parts, the first part is a 50 GHz (V band) power amplifier designed by CMOS 90 nm process. The output matching circuit is a transformer based impedance converter with a power combining structure. The second part is focused on the design of a GaN HEMT-based power amplifier with high efficiency and high linearity. The architecture is Doherty power amplifier, which is consisting of Class AB and Class C amplifiers.
In the first part, the output matching of the CMOS millimeter wave power amplifier using the characteristics of the transformer plays as a power combiner and impedance converter. As in the case of high impedance-conversion ratio, the loss of the traditional LC matching network will be higher, and the loss of transformer is independent on impedance conversion ratio. The transformer not only converts the impedance but also combine the deleivered power of two sets of differential amplifiers, and the simulated loss of the transformer is about 1.7 dB at 50 GHz. This power amplifier as measured at 50 GHz, the circuit gain is 7.8 dB, the output 1 dB gain compression point is 5.7 dBm, and the saturated output power of 10.2 dBm. The s-parameter measurement shows the gain being greater than 8 dB between 50 GHz and 67 GHz.
The second part of this thesis is the design of Doherty power amplifier. As the traditional power amplifier operation in the high efficiency region when the linearity is poor, otherwise, operating in the high linearity region, the efficiency of power amplifier will not be good. Doherty architecture uses active load modification at output port, and combines the characteristics of Class AB and Class C amplifier. So that the overall characteristic of power amplifier can maintain high efficiency without losing the linearity under the output power back off 6 dB from the saturation point. The measured result indicates that the third-order intermodulation distortion is lower than -30 dBc when the output power of the two-tone measurement is 36 dBm, and the one-tone output power is 37 dBm when the efficiency is 41.9 %.
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