26.3 A mm-Wave Power Amplifier for 5G Communication Using a Dual-Drive Topology Exhibiting a Maximum PAE of 50% and Maximum DE of 60% at 30GHz

Abstract

The mm-wave spectrum is opening a new opportunity for TRx systems to operate at high-Gb/s data-rates. However, this opportunity is also imposing stringent requirements for power amplifiers (PAs) in terms of efficiency and linearity. To this date, all PA designs focus on increasing the peak/power-back-off (PBO) PAE and output power $(max \mathrm{P}_{out})$ by either presenting multi-harmonic terminations or improving on existing topologies, such as stacked, outphasing, and Doherty PAs [1 –3]. However, in highly scaled silicon processes with low supply voltages, these reported techniques see diminishing returns on PAE and $\mathrm{P}_{out}$ since the transistor knee voltage $(\mathrm{V}_{knee})$ becomes a significant portion of the supply voltage [5]. Moreover, an extra reduction in supply voltage is often performed in practical deployment to ensure device reliability. This is especially relevant for mm-wave array operations, where array element couplings result in substantial antenna impedance mismatches and undesired large PA voltage swings [6]. Although the reported techniques have improved overall PA efficiency at mm-wave, fundamentally they are incapable of surpassing the theoretical PA core efficiency at the same conduction angle (e.g., Class-B common-source (CS) PA) without resorting to device switching, or harmonic shaping.