Fast Sensing Method Based on Beam Squint and Beam Split of Terahertz Reflective Intelligent Surfaces

HAO Wanming; YANG Lan; ZHU Zhengyu; LI Xingwang

doi:10.11999/JEIT240789

Volume 47 Issue 3

Mar. 2025

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Article Navigation > Journal of Electronics & Information Technology > 2025 > 47(3): 678-686

HAO Wanming, YANG Lan, ZHU Zhengyu, LI Xingwang. Fast Sensing Method Based on Beam Squint and Beam Split of Terahertz Reflective Intelligent Surfaces[J]. Journal of Electronics & Information Technology, 2025, 47(3): 678-686. doi: 10.11999/JEIT240789

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HAO Wanming, YANG Lan, ZHU Zhengyu, LI Xingwang. Fast Sensing Method Based on Beam Squint and Beam Split of Terahertz Reflective Intelligent Surfaces[J]. Journal of Electronics & Information Technology, 2025, 47(3): 678-686. doi: 10.11999/JEIT240789

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Fast Sensing Method Based on Beam Squint and Beam Split of Terahertz Reflective Intelligent Surfaces

doi: 10.11999/JEIT240789 cstr: 32379.14.JEIT240789

1.
School of Electrical and Information Engineering, Zhengzhou University, Zhengzhou 450001, China
2.
National Mobile Communications Research Laboratory, Southeast University, Nanjing 210096, China
3.
School of Physics and Electronic Information Engineering, Henan Polytechnic University, Jiaozuo 454000, China

Funds: The National Natural Science Foundation of China (62471440), The Open Research Fund of the National Mobile Communications Research Laboratory, Southeast University (2024D12)

Received Date: 2024-09-12
Rev Recd Date: 2025-02-17

Available Online: 2025-02-26

Publish Date: 2025-03-01

Abstract

Abstract

Objective Reﬂecting Intelligent Surface (RIS)-aided Terahertz (THz) communications are considered a key technology for future Sixth-Generation (6G) mobile communication systems addressing issues such as signal attenuation and Line-of-Sight (LoS) link blockage issues, due to their ultra-large bandwidth and low power consumption. However, the frequency independent characteristics of RIS elements can cause beam squint effects, where beams of different carriers are directed at different angles. Although this reduces the beam gain received by users, it can be leveraged to enhance sensing capabilities in sensing applications. Specifically, beam squint allows for simultaneous sensing of a target using multiple carrier beams directed in different directions. Existing studies have explored beam squint for beam training. For example, by studying near-field beam squint and True Time Delay (TTD) to generate beams that focus at multiple positions across different frequencies, enabling rapid beam training with reduced overhead. Additionally, combining TTD with beam squint and beam split for sensing extends the beam coverage area and enables the quick acquisition of user locations through feedback. However, there is no research on jointly utilizing beam squint and beam split for sensing in RIS-assisted THz systems. This paper aims to conduct detailed research on the use of beam squint for sensing in such systems. Methods To address the time-consuming issue of beam scanning in RIS-assisted THz systems, a fast sensing method based on RIS beam squint and split effects is proposed. Each RIS element is equipped with a TTD mechanism to dynamically adjust the degree of beam squint, while the large array RIS units are spaced to induce the beam split effect. By combining beam quint and beam split, the method enables rapid sensing of the target area. Specifically, the sensing area is divided into multiple sub-areas, with the TTD and the phase shift at the RIS elements optimized to cover each sub-area based on beam squint. The beam split effect is then used to seamlessly cover multiple sub-areas, significantly reducing time overhead compared to single beam scanning. To further mitigate echo signal path loss, active sensing elements are configured at the RIS for direct reception and analysis of the echo signals. The estimation of the sensing target’s angle, along with its Root Mean Square Error (RMSE), is derived based on this approach. Results and Discussions Consider the RIS-assisted THz sensing system model (Fig. 1). By deriving the channel and beam gain expressions, the beam patterns under the beam squint effect are analyzed (Fig. 2). Based on the internal structural diagram of the RIS (Fig. 4), the beam split effect is examined by varying the spacings between RIS elements (Fig. 5), with corresponding beam patterns (Fig. 3) presented for different spacings. Next, the RIS structure utilizing TTD (Fig. 6) allows for flexible adjustment of the beam squint and split degrees, significantly expanding the beam coverage area compared to traditional beam squint and split methods (Fig. 7, Fig. 8). Additionally, to fine-tune the gaps between adjacent split beams, the ATDS method is proposed. By combining beam squint and beam split, this method achieves near-seamless coverage of all subareas (Fig. 9). Finally, the target direction is estimated by analyzing the echo signals received at the RIS-SE, based on the RSME. The simulation results demonstrate the relationship between sensing accuracy and the number of carriers (Fig.10, Fig. 11), confirming the effectiveness and feasibility of the rapid sensing method combining beam squint and split. Conclusions This paper investigates the issues of beam squint and beam split in RIS-assisted THz systems and proposes a rapid sensing method that combines both effects. Specifically, TTD is used to adjust the direction of subcarrier beams based on beam squint. To expand the sensing area, the combined effects of beam squint and beam split, divide the sensing area into multiple subareas, which are simultaneously covered by multiple carrier beams within a single OFDM block. The target direction is then estimated based on echo signals received at the RIS-SE, with sensing error measured using the RMSE between the true and estimated values. Simulation results demonstrate the feasibility and effectiveness of the proposed rapid sensing method. However, it is found that while the beam squint effect significantly reduces beam gain and communication performance, it expands the beam coverage area and enhances sensing capabilities. Therefore, in an integrated sensing and communication system, the impact of beam squint should be considered at different stages. Future research will focus on improving the performance of such integrated systems.
- Terahertz (THz),
- Reflecting Intelligent Surface (RIS),
- Beam squint,
- Beam split,
- Fast sensing

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References(15)

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