| Summary: | 碩士 === 國立中興大學 === 電機工程學系 === 89 === With the rapid developments of wireless communication , Power Amplifiers (PA) not only require high output power, power-added efficiency, but also high linearity. For the performance of power amplifiers, the most important components are the power devices we used. The most widely used power devices are PHEMT and HBT now. Therefore this thesis focuses on the characteristics of PHEMT and HBT and performs several power measurements. In addition, we analyze the gain compression mechanism and different impedance load lines.
This thesis is divided into three subjects. The first subject is the basic concepts of power measurement and load impedance. In the second subject we analyze the gain compression of PHEMT, such as knee voltage, pinch-off voltage, breakdown voltage, the maximum drain current and other characteristics. In the last subject we study the most important power device, HBT. HBT have very different bias operation and gain compression mechanism from PHEMT, such as Class-A operation, knee voltage, beakdown voltage, constant base voltage.
In this thesis, we carefully analyze the power characteristics of these power devices in detailed and develop a new peculiar way to characterize the different gain compression mechanism. The influence of power in different load lines is also studied.
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