A Wideband Class-AB Power Amplifier With 29–57-GHz AM–PM Compensation in 0.9-V 28-nm Bulk CMOS

A wideband amplitude to phase (AM-PM) compensated class-AB power amplifier (PA) suitable for highly integrated fifth-generation phased arrays is designed in 0.9-V 28-nm CMOS without RF ultra-thick top metal. Design techniques to realize broadband impedance transformation, power division/combining, and phase distortion linearization are discussed. Further, second-order effects due to practical layout constrains imposed by deep-scaled technologies are addressed and simple design solutions are proposed. The designed PA shows a measured S21-3 dB bandwidth (BW) from 29 to 57 GHz (65%) with |AM-PM|56% BW-1 dB, with a peak power added efficiency of 24.2%. When a signal with wide modulation BW is applied, the realized PA enables up to 10.1-, 8.9-, and 5.9-dBm average POUT while amplifying a 1.5-, 3-, and 6-Gb/s 64-quadratic-amplitude modulation, respectively, at 34 GHz. The in-band and out-of-band linearity measured in error vector magnitude and adjacent channel power ratio are always better than -25 dB and -30 dBc, respectively, without any digital pre-distortion.