A high power, high efficiency UMTS amplifier using a novel Doherty configuration

The majority of prior publications on high efficiency amplifiers employing the Doherty configuration have described relatively low peak power circuits. Much of the previously published work has employed Si CMOS, GaAs MESFET or HBT technologies at RF power levels of, at most, a few watts suitable for mobile handset applications. This paper describes a novel Doherty amplifier configuration employing packaged Si LDMOS FETs. The main emphasis has been on providing acceptable gain, flatness, efficiency and linearity over the full UMTS band of 2.11 to 2.17 GHz at single circuit power levels of 90 watts. At 8 dB back-off from P1dB this amplifier configuration has achieved close to 33% drain efficiency under 2 carrier W-CDMA conditions compared to a reference drain efficiency of approximately 20 to 23% under the same ACPR and ACLR conditions for a single, 90 W, discrete transistor amplifier.