| WCDMA is one of four the whole world 3G standards that International Telecommunication Union approves. WCDMA relies on it's bigger system capacity , more excellent implication mass , higher frequency spectrum efficiency , quicker data rate, stronger anti-fading ability, much better resisting. It will become the best mutipleaccess scheme of IMT-2000/UMTS. The linearity requirement of the base station power amplifier becomes tighter because of spectrum emission. On consider of the cost and rejection of heat of base station, the efficiency is also a critical factor when linearity is enough.This paper firstly analyses the unlinearity characteristic of power amplifier and linear technologys especial feedforward technique in theory. At the same time, it introduces a novelty feedforward technology which well make up the lower efficiency of traditional feedforward technology. According to the RF specifications in 3GPP for WCDMA transmitter power amplifier, an adaptive feedforward amplifier system is completed including EDA simulation, circuits layout and main mechanical structure design.Test results show that under 2-tone test in 5MHz tone spacing, the power amplifier system achieves near upon -50dBc .Though there is a little worse in linearity of the feedforward system, it theoretically satisfies the 3GPP requirement for WCDMA base-station transistor.The efficiency of the whole feedforward system is quite improved compared to that of traditional feedfarward system. |
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