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There is a growing demand for the implementation of the RF power amplifier (PA) in CMOS technologies, due to its cost and integration benefits. Most of the already reported CMOS PAs do not have sufficient output power nor linearity to cope with the long term evolution (LTE) requirements. In this paper, the linearity requirements for power amplifiers targeting LTE-applications are investigated. Based on this system level analysis, a single-chip fully integrated CMOS power amplifier with sufficient power and linearity for emerging E-UTRA/LTE-applications is designed. This 90-nm LTE-band VIII CMOS linear power amplifier uses a distributed active transformer (DAT) as power combiner and delivers an output power up to 29.4 dBm with 25.8% power-added efficiency (PAE) and has 28-dB small-signal gain. The choice of optimal biasing ensures a very flat gain and small AM-PM distortion up to high output power. While applying an uplink LTE signal, the PA produces 25 dBm of average output power with 15% PAE while obeying the stringent EVM-specifications.
Microwave Theory and Techniques, IEEE Transactions on (Volume:60 , Issue: 6 )
Date of Publication: June 2012