A 1.9-GHz CMOS Power Amplifier Using Three-Port Asymmetric Transmission Line Transformer for a Polar Transmitter

Abstract

A 1.9-GHz CMOS differential power amplifier for a polar transmitter is implemented with a 0.18-m RF CMOS process. All of the matching components, including the input and output transformers, are fully integrated. The concepts of injection locking and variable load are applied to increase the efficiency and dynamic range of the amplifier. An asymmetric three-port transmission line transformer is proposed to embody the variable load effectively. The power amplifier achieved a power-added efficiency of 40% at a maximum output power of 32 dBm. The dynamic range was 20 dB at supply voltages ranging from 0.5 to 3.3 V. The improvement of the low power efficiency was 290% at an output power of 16 dBm.Index Terms-Class-E, CMOS, dynamic range, global system for mobile communication (GSM), injection locking, polar transmitter, power amplifier, transmission line transformer, variable load.

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“…Given that, statistically, the power transmitted in a wireless system is below the maximum for most of the transmission time, the average power efficiency is far below its maximum. It is, therefore, essential to maintain a high level of efficiency over a wide range of output power when seeking to enhance the average power efficiency [4][5][6][7][8].…”

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