Adapting the Doherty amplifier for millimetre-wave CMOS applications

This paper investigates the difficulties of implementing a Doherty power amplifier (DPA) in CMOS at millimetrewave (mm-wave) frequencies. A simplified circuit-level model of the Doherty is proposed to study the performance limitations of deep sub-micron technologies, namely the output impedance, knee voltage, and breakdown voltage. Subsequently, the trends found with the model are used to implement a reconfigurable DPA at E-band frequencies in a commercially available 90-nm RF-CMOS process. The DPA consumes 21.7 mA from 1.5 V and produces 11.7 dBm of output power at P1dBwith a PAE of 30.6 % and a 6-dB back-off PAE of 15.6 %. The reconfigurable option is bias controlled and improves the gain by 3.2 dB while increasing the current consumption by 7.1 mA. The circuit footprint is 1.53 mm2 and the efficiency characteristics are within 5 % of the model prediction