摘要：近日，大连理工大学赵明山、韩秀友团队以「Silicon photonic integrated wideband radio frequency self-interference cancellation chip for over-the-air in-b
近日，大连理工大学赵明山、韩秀友团队以「Silicon photonic integrated wideband radio frequency self-interference cancellation chip for over-the-air in-band full-duplex communication」¹为题在Chip上发表研究论文，利用硅光集成平台研制出宽带光子射频自干扰消除芯片。第一作者为苏鑫鑫，巢萌为共同第一作者，通讯作者为韩秀友。本文被遴选为本期Featured in Chip编辑特选文章之一。Chip是全球唯一聚焦芯片类研究的综合性国际期刊，是入选了国家高起点新刊计划的「三类高质量论文」期刊之一。
无线通信技术的快速发展使得频谱资源日趋紧张，如何提升频谱利用效率是B5G和6G通信面临的重要挑战。同时同频全双工技术与传统的频分双工和时分双工相比，能使频谱利用效率和信息传输速率倍增2，极具技术优势和应用前景。然而，射频自干扰是全双工技术实际应用必须解决的关键问题。光子射频自干扰消除技术具有工作频段范围宽、带宽大、幅度和延时调节精度高、抗电磁干扰等优点3。新一代移动通信终端和卫星载荷等对射频自干扰消除系统提出了小型化、集成化和低功耗的要求4-6。本文提出片上直流偏置相位调控，结合光域延时连续可调和幅度大动态调节的光子射频对消方案，基于硅光集成平台研制出光子射频自干扰消除芯片，进行了无线全双工通信的实验验证。
图1 | 硅基集成光子射频自干扰消除芯片方案。a，光子射频自干扰消除方案原理图。b，集成光子芯片结构示意图。c，制备出的芯片照片及光学显微镜图片。
本文提出的片上集成光子射频对消方案如图1a所示，通过直流调控强度调制器（Mach–Zehnder Modulator，MZM）MZM1和MZM2分别处于偏置正交点的正、负斜率处，实现参考信号与干扰信号的相位反相，通过光幅度调节器（Optical amplitude Adjuster，OAA）与可调光延时线（Tunable Optical Delay Line，TODL）实现光域微波信号的幅度和延时调节，当参考信号与干扰信号满足相位反相、幅度相等和延时匹配条件，二者合路经光电转换后实现相干相消，干扰信号被消除，有用信号恢复出来。图1b为集成芯片的结构示意图，强度调制器采用单端推挽式马赫-曾德尔干涉（Mach-Zehnder Interferometer，MZI）结构。光幅度调节器采用2×2多模干涉（Multimode Interferometer，MMI）构成等臂长MZI结构，基于热光移相机制实现光域微波的幅度调节，并在热光电极两侧添加热隔离槽以提升热光调节效率和降低对相邻波导的热串扰。可调光延时线采用6-bit光开关切换波导与热光调控长螺旋波导构成，可实现0~64 ps范围的延时连续调节。参考信号和干扰信号通过光耦合器（Optical Coupler，OC）合路，传输至光电探测器（Photodetector，PD）中完成光电转换。制备出的硅基集成光子射频自干扰消除芯片如图1c所示，片上系统的尺寸为4 mm×2.1 mm。
图2 | L~Ka波段范围光子射频自干扰消除性能的表征。
对研制的芯片进行了光、直流和射频封装，并对射频自干扰消除性能进行了测试表征，结果如图2所示。工作频段覆盖了L~ka波段，在S~C波段实现了4.8 GHz带宽高于20 dB的消除深度。在2 GHz中心频率处80 MHz带宽实现了大于40 dB的消除深度。建立了带内全双工无线通信实验系统（如图3a所示），对芯片模块的干扰消除能力进行了测试验证，结果如图3b所示，在5G通信的6 GHz中心频率处，100 MHz带宽实现了21.7 dB的干扰消除深度，成功恢复出有用信号。
图3 | 全双工无线通信功能验证。a，全双工无线通信测试系统。b，干扰消除前后信号的频谱图以及有用信号的星座图。
综上所述，本文对片上集成光子射频自干扰消除系统进行了优化设计，研制出硅光集成芯片，测试了该芯片的射频自干扰消除以及全双工无线通信的功能，验证了光子射频对消技术的宽频段、大带宽和高干扰消除深度的能力。研究工作为同时同频全双工技术的应用提供了小型化、集成化和低功耗的射频自干扰消除方案。
Silicon photonic integrated wideband radio frequency self-interference cancellation chip for over-the-air in-band full-duplex communication¹
The rapid development of wireless communication technology has made spectrum resources increasingly scarce, and how to improve spectrum utilization efficiency is a severe challenge faced by B5G and 6G communication. Compared with the traditional frequency division duplex and time division duplex, the in-band full-duplex (IBFD) technology can double spectrum utilization efficiency and information transmission rates2, exhibiting substantial technical advantages and application prospects. However, the radio frequency (RF) self-interference is a crucial issue that must be addressed for the real application of IBFD technology. Photonics RF self-interference cancellation (SIC) technology boasts a wide operating frequency range, large bandwidth, high precision in amplitude and time delay adjustment, and electromagnetic interference immunity3. The new generation of mobile terminals and satellite payloads have put forward the requirements of miniaturization, integration and low power consumption for RF SIC system4-6. In this paper a new on-chip photonics RF SIC scheme is proposed by utilizing the direct current (DC) bias phase control, combined with the continuously adjustable delay and large dynamic amplitude adjustment in the optical domain. Based on the silicon photonics integrated platform, a photonics RF SIC chip is developed, with which the over-the-air IBFD communication is demonstrated experimentally.
Fig. 1 | RF self-interference cancellation scheme by using the silicon photonics integrated chip.a, The photonics RF self-interference cancellation schematic with intensity modulation. b, Structural schematic of the integrated photonics RF SIC chip. c, Photograph and optical microscopeimages of the fabricated silicon photonics RF SIC chip.
The proposed on-chip integrated photonics RF SIC scheme is illustrated in Fig. 1a. It achieves phase inversion between the reference and interference signals by biasing the intensity modulators (MZM1 and MZM2) at the positive and negative slopes of the quadrature points, respectively. The optical amplitude adjusters (OAAs) and tunable optical delay lines (TODLs) are utilized to adjust the amplitude and delay of microwave signals in the optical domain. When the reference signal and interference signal meet the conditions of phase inversion, equal amplitude, and matched delay, they cancel with each other after photoelectric conversion. The interference signal is eliminated and the useful signal is recovered. Fig. 1b depicts the structural schematic of the integrated chip, where the intensity modulators adopt a single-ended push-pull Mach-Zehnder interferometer (MZI) structure. The OAA employs a 2×2 multimode interferometer (MMI) to form an equal-arm MZI structure, realizing amplitude adjustment of microwave signals by the thermal-optic phase shifting mechanism. Thermal isolation grooves are added on both sides of the thermal-optic electrodes to enhance thermal regulation efficiency and reduce thermal crosstalk to adjacent waveguides. The TODL consists of a 6-bit switched waveguides and a thermal-optic controlled long spiral waveguide, enabling continuous delay adjustment from 0 to 64 ps. The reference signal and interference signal are combined through an optical coupler (OC) and transmit to a photodetector (PD) for photoelectric conversion. The fabricated silicon-based integrated photonics RF SIC chip is shown in Fig. 1c, with the footprint of 4 mm×2.1 mm.
Fig. 2 | Characterization of photonics RF self-interference cancellation performance in the L~Ka band.
Thefabricated chip was packaged with optical, DC and RF, and the RF SIC performance were tested and characterized, with the results shown in Fig. 2. The operating frequency band covers the L to Ka bands, achieving a cancellation depth exceeding 20 dB across a 4.8 GHz bandwidth over the S to C bands. At a center frequency of 2 GHz, a cancellation depth greater than 40 dB is achieved within an 80 MHz bandwidth. An IBFD wireless communication experimental system (as shown in Fig. 3a) was established to test and verify the RF SIC capability of the chip module. The results are shown in Fig. 3b, at the center frequency of 6 GHz for 5G communication, a cancellation depth of 21.7 dB is achieved within a 100 MHz bandwidth, and the useful signal was recovered successfully.
Fig. 3 | The demonstration of the over-the-air in-band full-duplex communication by using the packaged photonics RF SIC chip. a, The test system for the over-the-air in-band full-duplex communication. b, Measured RF spectra with and without cancellation, and the insets are the corresponding constellation diagrams of the recovered signal of interest.
In summary, this paper presents an on-chip integrated photonics RF SIC system for IBFD communications. A silicon photonics integrated chip has been designed, fabricated and tested for the RF SIC and IBFD wireless communication functions. The ability of photonics RF SIC technology to achieve a wide frequency band, large bandwidth, and high interference cancellation depth has been verified with experimental results. The work provides a miniaturized, integrated, and low power consumption RF self-interference cancellation solution for the application of in-band full-duplex technology.
参考文献
1. Su, X. et al. Silicon photonic integrated wideband radio frequency selfinterference cancellation chip for over-the-air in-band full-duplex communication. Chip3, 100114 (2024).
2. Sharma, S. et al. Dynamic spectrum sharing in 5G wireless networks with full-duplex technology: recent advances and research challenges. IEEE Commun. Surv. Tutorials20, 674–707 (2018).
3. Han, X. et al. RF self-interference cancellation by using photonic technology. Chin. Opt. Lett.19, 73901 (2021).
4. Shu, H. et al. Microcomb-driven silicon photonic systems. Nature605, 457–463 (2022).
5. Pandey, A., Gasse, K. & Thourhout, D. Integrated photonics approach to radio-frequency self-interference cancellation. Opt. Contin.1, 1668–1675 (2022).
6. Han, X. et al. Integrated photonic RF self-interference cancellation on silicon platform for full-duplex communication. Photon. Res.11, 1635–1646 (2023).
论文链接：
作者简介
苏鑫鑫，2023年毕业于大连理工大学获得光学工程博士学位，目前就职于重庆联合微电子中心（CUMEC），任研发工程师，研究方向为光电集成芯片和微波光子信号处理技术。
Xinxin Su received the Ph.D. degree in optical engineering from Dalian University of Technology, China, in 2023. She is currently a R&D engineer in Chongqing United Microelectronics Center, CUMEC, China. Her research interests include integrated optoelectronic technology and microwave photonic signal processing.
巢萌，目前在大连理工大学攻读光学工程专业博士学位，研究方向为集成微波光子技术。
Meng Chao is currently a Ph.D. candidate of optical engineering in Dalian University of Technology, China. Her research interest focuses on integrated microwave photonic technology.
韩秀友，大连理工大学教授，博士生导师。大连理工大学「信息光电子技术」科研创新团队核心成员，担任光电工程与仪器科学学院副院长，辽宁省先进光电子技术重点实验室副主任。入选兴辽英才计划科技领军人才、辽宁省高校创新人才计划，荣获辽宁省优秀教师、辽宁省首届优秀研究生导师等荣誉称号。长期致力于微波光子学和集成光子学领域的研究，主持和参加国家基金重点项目、国家重点研发计划课题、国家自然科学基金面上等多项课题。在Chip，Photonics Research, Optics Letters, Journal of Lightwave Technology等光电领域知名期刊和国际会议上发表论文100余篇。授权中国发明专利30余项，美国发明专利2项。
Xiuyou Han is a Full Professor in Dalian University of Technology, China, the core member of the 「Information Optoelectronic Technology」 research and innovation team. He is the Deputy Dean of the School of Optoelectronic Engineering and Instrument Science, DUT, and the Deputy Director of the Liaoning Provincial Key Laboratory of Advanced Optoelectronic Technology. He was the recipient the Leading Talent of Science and Technology of Liao Ning Revitalization Talents Program, the Innovative Talent in Universities of Liaoning Province, the Outstanding Teacher in Liaoning Province，the Excellent Graduate Supervisor of Liaoning Province. He has been engaged in the research of microwave photonics and integrated photonics. He presided over and participated in many projects, such as the Key Project of National Field Foundation, the National Key Research and Development Plan, and the National Natural Science Foundation, etc. He has authors more than 100 papers in well-known journals and international conferences in the field of optoelectronics. He has been authorized over 30 invention patents in China and 2 invention patents in the United States.
赵明山，大连理工大学，教授，博士生导师。大连理工大学「信息光电子技术」科研创新团队带头人，国家重点创新项目首席，享受国务院政府特殊津贴专家，大连市「领军人才」，「辽宁省先进光电子技术重点实验室」主任，大连理工大学光子技术研究中心主任。长期从事信息光电子技术领域的研究工作，重点开展微波光子技术、集成光子芯片与器件、光电融合感知与应用研究。科技成果曾获国家科技进步二等奖等省部级以上奖励3项。在国际和国内重要学术期刊发表学术论文120余篇，出版学术专著二部。
Mingshan Zhao is a Full Professor in Dalian University of Technology, China. He is the leader of the 「Information Optoelectronic Technology」 research and innovation team at Dalian University of Technology, the chief scientist of a national key innovation project, the expert with special government allowances from the State Council of China, the 「Leading Talent」 in Dalian, the director of the 「Liaoning Province Key Laboratory of Advanced Optoelectronic Technology」, and the director of the Photonics Research Center at Dalian University of Technology. He has mainly been involved in long-term research in the field of information optoelectronic technology, with a focus on microwave photon technology, integrated photonic chips and devices, optoelectronic integration sensing and applications. He has been awarded the second prize of National Science and Technology Progress Award and other provincial and ministerial level for 3 items. He has published more than 120 papers in peer-reviewed journals and two academic monographs.
关于Chip
Chip（ISSN：2772-2724，CN：31-2189/O4）是全球唯一聚焦芯片类研究的综合性国际期刊，已入选由中国科协、教育部、科技部、中科院等单位联合实施的「中国科技期刊卓越行动计划高起点新刊项目」、「中国科技期刊卓越行动计划二期项目-英文梯队期刊」，为科技部鼓励发表「三类高质量论文」期刊之一。
Chip期刊由上海交通大学出版，联合Elsevier集团全球发行，并与多家国内外知名学术组织展开合作，为学术会议提供高质量交流平台。
Chip秉承创刊理念: All About Chip，聚焦芯片，兼容并包，旨在发表与芯片相关的各科研领域尖端突破性成果，助力未来芯片科技发展。迄今为止，Chip已在其编委会汇集了来自14个国家的69名世界知名专家学者，其中包括多名中外院士及IEEE、ACM、Optica等知名国际学会终身会士（Fellow）。
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来源：Future远见
