Transformer-Based Doherty Power Amplifiers for mm-Wave Applications in 40-nm CMOS

This paper presents a power amplifier (PA) topology to improve the back-off efficiency and the linearity of millimeter-wave (mm-wave) PAs without area overhead. In this paper, an asymmetrical series power combiner with LC tuning circuits is proposed to mimic the Doherty operation. Due to high back-off efficiency and high linearity behavior, the proposed Doherty topology well suits for E-band communication applications. Two transformer-based E-band PAs are designed and measured to demonstrate the proposed mm-wave Doherty concept. The first implementation achieves 16.2-dBm output power with a P1dB of 15.2 dBm using a 0.9-V supply. The second implementation demonstrates 21-dBm output power with a power-added efficiency (PAE) of 13.6% at a 1.5-V supply. The PAE at 6-dB power back-off is still as high as 7%.