A Transformer-Based Quadrature Doherty Digital Power Amplifier With 4.1 W Peak Power in 28 nm Bulk CMOS

This article presents an 8-way serial power combined transformer-based quadrature digital power amplifier (DPA) with in-phase/quadrature (IQ)-reuse and Doherty techniques for high output power and high efficiency. An 8-way serial-combining transformer (SCT) power combiner is employed to achieve 4.1 W (36.1 dBm) peak output power. IQ-reuse and transformer-based Doherty techniques are adopted to enhance the efficiency at 3 and 6 dB power back-offs (PBOs). Implemented in 28 nm CMOS and powered by 1.1 and 2.2 V supply voltages, this quadrature DPA achieves >30% peak power-added efficiency (PAE) across 2.7–3.2 GHz and its 1 dB radio frequency (RF) bandwidth ranges from 2.6 to 3.2 GHz. Besides, it obtains the PAE of 25.3% and 22.6% at 6 and 3 dB PBOs, respectively. For long term evolution (LTE) 20 MHz 64 quadratic amplitude modulation (QAM) signal, this DPA achieves 29.4 dBm average output power, 18.5% average PAE at −25 dB error vector magnitude (EVM) limit, and it realizes almost 60 dB dynamic power range from −30 to 29.4 dBm with EVM below −25 dB at 2.9 GHz.