The Design And Fabrication Of Signal Pre-processing Subsystem Applied In Adaptive Feedforward Power Amplifier

In the system of modern wireless communication, the transmission of information is developing toward multi-carrier, great-capacity and high-speed. This needs the RF components to provide higher linear in the systems of communication. Especially the linearity of power amplifier will affect the performance of the whole system. Feed-forward power amplifiers are more concerned by RF engineers because of its high linearity and stability. As the emerging of high performance digital signal processing devices such as digital signal processor (DSP) and field programmable gate array (FPGA) , the software defined radio (SDR) based Digital IF technology has been widely used in linearizing technology of the amplify recently.In chapter one and two, the author makes a systematic exposition of the origin and concept of the software radio which includes the basic structure and main features of software radio, summarizes several key technologies of software radio, such as wideband A/D converter, numerical controlled oscillator (NCO), and high speed digital signal processing. The paper clarifies the basic concept of the digital down-converter, and it also gives the comparison of several different digital down-converter chips and simply summarizes the digital down-converter. In chapter three, the paper introduces the configuration of the digital intermediate frequency pre-processing in the adaptive feedforward power amplifier used in the WCDMA. It also describes the performance and the function that the system should achieve. Then the digital intermediate frequency pre-processing in the adaptive control module based on the SDR is optimized, and one specific design based on software defined radio is given too. In the end, the paper describes the problems meet in the debugging and the ways to resolve. Then it gives the result of the performance measure which proves that the design matches the requirements.The digital intermediate frequency pre-processing is one of the novel key techniques of adaptive control feed-forward power amplifier, and it influences the performance of the whole system. The analysis and the measure results both prove that the digital intermediate frequency pre-processing technology based on the SDR is mature. It will take an important effect in the research and the development of the adaptive feedforward power amplifier.