题目：Near-Field Beamfocusing: From Theory to Practice

摘要：As the element count increases in antenna arrays and the carrier frequency rises, a new operating regime emerges: the radiative near-field. It spans a distance range where the reactive near-field effects are negligible, but the wavefronts remain noticeably curved. This differs from the traditional far-field scenario experienced in current systems, where the received signal consists of a superposition of planar wavefronts. The wave curvature presents opportunities for both novel applications and beam design, beyond current practices. The near-field topic has been studied for several decades, from various perspectives, but has gained momentum in recent years. The primary example is finite-depth beamfocusing, which enables signals to be focused into ellipsoidal regions, confined in both angle and distance.

In this talk, we will first go through the theoretical properties of radiative near-field propagation, including different ways to define the radiative near-field, beamfocusing, Bessel beams, and their relation to spatial frequencies. We will examine which features have been experimentally validated and the hardware-related practical implementation challenges that these experiments reveal. Finally, we identify the most promising use cases for near-field effects to enhance communication, localization, and sensing in 6G systems. There is no one-size-fits-all solution, but a toolbox of features suitable for different purposes.

时间：2026年7月10日，10:00-11:00

地点：紫金山实验室二楼报告厅2

个人简介：

Emil Björnson is a Professor of Wireless Communication at the KTH Royal Institute of Technology, Stockholm, Sweden. He is an IEEE Fellow, Digital Futures Fellow, Wallenberg Academy Fellow, and Clarivate Highly Cited Researcher. He has a podcast and YouTube channel called Wireless Future. His research focuses on multi-antenna communications and radio resource management, using methods from communication theory, signal processing, and machine learning. He has authored four textbooks and published 70 simulation code repositories.

He has received the 2018 and 2022 IEEE Marconi Prize Paper Awards in Wireless Communications, the 2019 EURASIP Early Career Award, the 2019 IEEE Communications Society Fred W. Ellersick Prize, the 2019 IEEE Signal Processing Magazine Best Column Award, the 2020 Pierre-Simon Laplace Early Career Technical Achievement Award, the 2020 CTTC Early Achievement Award, the 2021 IEEE ComSoc RCC Early Achievement Award, the 2023 IEEE ComSoc Outstanding Paper Award, and the 2024 IEEE Stephen O. Rice Prize.