JSSC 2023第12期RF & Wireless28nmPower Amplifier

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

采用8路串联变压器和IQ重用技术的Doherty数字功率放大器，实现高输出功率和高效率。

28 nm CMOS, 1.1/2.2 V, 4.1 W (36.1 dBm) peak output power, >30% peak PAE, 2.7–3.2 GHz

数字功率放大器Doherty技术IQ重用功率合成器高效率

▸创新点1：8路串联变压器功率合成器（电路创新）——通过8路串联变压器功率合成器，实现了4.1 W的峰值输出功率，显著提升了功率放大器的输出能力，同时优化了功率合成的效率和带宽性能。

▸创新点2：IQ重用技术（方法创新）——采用IQ重用技术，有效提高了功率放大器在3 dB和6 dB功率回退点的效率，优化了信号处理路径，减少了资源浪费，提升了整体系统性能。

▸创新点3：基于变压器的Doherty技术（电路创新）——结合变压器技术实现Doherty架构，进一步提升了功率放大器在功率回退点的效率，特别是在3 dB和6 dB回退点分别实现了22.6%和25.3%的功率附加效率（PAE）。

▸创新点4：宽动态范围与高效率（系统创新）——在2.9 GHz频率下，实现了近60 dB的动态功率范围，且在LTE 20 MHz 64 QAM信号下，达到了29.4 dBm的平均输出功率和18.5%的平均PAE，同时满足EVM低于-25 dB的高线性度要求。

Abstract

This article presents an 8-way serial power com- bined transformer-based quadrature digital power amplifier (DPA) with in-phase/quadrature (IQ)-reuse and Doherty tech- niques 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) band- width 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.