| The modern wireless communication technologies require a system that could support high information transfer rate, tend to use non-constant envelope modulation and frequency division multiplexing. So the wireless signals (for example WCDMA, OFDM) have a higher PAPR. But this kind of signal requires that the power amplifier (PA) have a wider linear region. Power back-off is often used in traditional PA to avoid from signal distortion when it surpasses the linear region. The problem is, it will reduce the efficiency of PA. How to increase the efficiency of PA becomes the most important problem.A lot of methods have been put forward to solve this problem. Envelope Tracking (ET) power amplifier is the most concern one. ET amplifier is adjusting the bias voltage based on the envelope tracking to reduce the power loss of PA when there is a small envelope input, it has a great research value.In this dissertation, we analyze and research the key technologies of the wideband ET amplifier system, to achieve the goal of improving the efficiency of high PAPR wideband signal power amplifier.First, we give the basic structure of analog-control ET amplifier system and analyze the key technologies of the ET amplifier system.Then, we focus on the high efficiency wideband envelope amplifier which is critical to the realization of ET amplifier. A slip-band envelope amplifier is designed for the 802.11g signal. We illustrated its operation principle, analyzed its some kinds of operation state, optimized circuit parameter according to the simulation of its behavior model. The simulation shows that its efficiency is 65% and bandwidth is 20MHz when 802.11g signal envelope inputs.Finally, a wideband ET system is designed on the base of front chapters. Contracting to the 12% PAE of the fixed bias power amplifier at the 20dBm output power, ET system can be as high as 26%.The result shows that the ET system given in the dissertation is feasible. It lays a foundation of non-constant signal power amplifier, which is of great theoretical importance and economic value. |
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