As demand for ultrafast wireless connectivity grows ⎯ from telemedicine to streaming high-definition videos ⎯ society faces a significant roadblock: power-hungry electronics that make high-speed networks like 5G expensive and inefficient to operate.
At the heart of this challenge lies the power amplifier, a critical building block of a wireless device that strengthens a signal before radiating it through an antenna. In 5G and emerging beyond-5G systems, especially those operating in the millimeter-wave range ⎯ a portion of the radio frequency (RF) spectrum that enables very rapid data transfer ⎯ traditional power amplifiers drain a lot of energy.
A team of Rice University electrical engineers led by Taiyun Chi developed a new kind of power amplifier that combines cutting-edge design in both circuitry and electromagnetics. Their innovation ⎯ known as a multiway Doherty power amplifier ⎯ delivers unprecedented efficiency even under demanding, high-speed conditions. The amplifier prototype is the first of its kind in silicon to support an ultrawide 2,000-megahertz channel bandwidth, a core requirement of advanced 5G standards.
“Our new amplifier design offers significant gains in terms of efficiency, size and bandwidth,” said Chi, assistant professor of electrical and computer engineering.
The Rice team’s breakthrough builds upon the foundational Doherty power amplifier architecture named after its inventor, Bell Labs engineer William Doherty, who developed the architecture in 1936. Unlike traditional amplifiers that operate best only at peak output, Doherty amplifiers are designed to handle complex communication waveforms and typically consist of two paths ⎯ a main path that handles lower power levels and an auxiliary path for high-power surges.
Most existing Doherty implementations are characterized by a “two-way” architecture, which struggles with handling highly dynamic signals such as those used in 5G and Wi-Fi systems. That is where Rice researchers’ multiway Doherty design comes in: using three or more amplifier paths for greater flexibility and efficiency across a broader range of signal conditions.
While similar attempts had been made in the past to improve upon the basic Doherty amplifier, “our approach was based on a deeper, rigorous analysis of how current and voltage profiles are established within the amplifier,” Chi said.
“This analysis allowed us to come up with a systematic method to extend a traditional two-way Doherty amplifier to multiple ways while ensuring true multiway Doherty load modulation, significantly enhancing efficiency enhancement.”
In addition to efficiency, another major challenge is size: By leveraging RF circuit design innovations, the researchers drastically reduced the size of the power amplifier, making it small enough to integrate into the tiny chips that power smartphones and base stations alike. This compact design opens the door for large-scale deployment in consumer devices.
Another key innovation is a high-speed adaptive biasing circuit. While adaptive biasing used to control the auxiliary path is crucial in Doherty amplifiers, it often limits the amplifier bandwidth.
“Our idea was simple yet effective,” Chi said. “By adding a compact inductor to the conventional adaptive biasing circuit, we nearly doubled the bandwidth.”
The amplifier’s high efficiency, compact footprint and broad bandwidth make it ideal not only for 5G base stations and mobile devices but also for emerging applications in satellite communications, where energy conservation and rapid data transmission are critical.
The research won the 2024 Lewis Winner Outstanding Paper Award, which was announced at the 2025 International Solid-State Circuits Conference (ISSCC) last month. The award is based on ratings by conference attendees in the previous year.
“Our hope is that these advancements in circuit theory and new topology development will empower and inspire future research on power amplifier and transceiver systems needed for next-generation wireless,” Chi said.
The research was supported by GlobalFoundries, which provided the chip fabrication used in the research.
- Peer-reviewed conference paper:
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“A 47GHz 4-way Doherty PA with 23.7dBm P1dB and 21.7% / 13.1% PAE at 6 / 12dB Back-off Supporting 2000MHz 5G NR 64-QAM OFDM,” IEEE International Solid-State Circuits Conference (ISSCC), 2024
Authors: Xiaohan Zhang, Hao Guo and Taiyun Chi
https://ieeexplore.ieee.org/abstract/document/10454571 - Journal extension:
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“A Millimeter-Wave Four-Way Doherty Power Amplifier With Over-GHz Modulation Bandwidth,” IEEE Journal of Solid-State Circuits (JSSC), 2024
DOI: 10.1109/JSSC.2024.3453321
https://ieeexplore.ieee.org/abstract/document/10675497