This paper presents a high efficiency feedforward power amplifier with Doherty technique for multi-carrier GSM base-station. The main Doherty power amplifier (DPA) was designed with third-order intermodulation distortion (IMD3) cancellation technique and tunable power division for optimized linearity and efficiency. The error amplifier was selected based on IMD3 analysis for higher efficiency. Two tone test show the amplifier has an efficiency of 27.2% and an IMD3 below -62.5dBc at 80W overall output power, the efficiency is much higher than traditional feedforward amplifiers.

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In this article, a frequency-regeneration type divide-by-3 FD with quadrature signal outputs is presented. This chip is implemented using TSMC 0.18-lm CMOS technology. Outputs of ILFD are mixed with the input signal to regenerate the required division ratio. The current reuse technique is adopted to save the power consumption. Measured results show that the free-running frequency is from 1.173 to 1.25 GHz. The proposed FD can cover the input frequency from 3.51 to 3.8 GHz at the incident power of À3 dBm. This core circuit draws a 12 mA current from a 1.8 V power supply. ACKNOWLEDGMENTS