太赫兹无线和有线融合通信技术的研究与展望

随着5G的移动互联及物联网相交织等新型业务的蓬勃发展,对未来通信系统传输容量、传输速度以及误码率等要求愈来愈高。介于毫米波与远红外光之间的太赫兹频段兼有微波和光波的特性,具有低量子能量、大带宽、良好的穿透性。近年来太赫兹通信系统成为研究热点之一,但太赫兹无线通信存在视距传播以及较大路径损耗缺点,太赫兹无线和有线融合传输则兼具两者优点。本文分析了光子太赫兹信号产生、光子太赫兹无线链路传输和光子太赫兹光纤链路传输过程中涉及的器件和技术,重点介绍了太赫兹有线传输的研究现状,并通过基于强度调制直接检测实现1.485 GBaud 350 GHz的1 m太赫兹光纤有线实时传输视频实验,展现了太赫兹有线传输巨大的发展潜力。     

超宽带太赫兹调频连续波成像技术

太赫兹调频连续波成像技术具有高功率、小型化、低成本、三维成像等特点,在太赫兹无损检测领域受到了广泛关注。然而由于微波及太赫兹器件限制,太赫兹信号带宽难以做大,从而制约了成像的距离向分辨力。虽然高载频可实现较大宽带,但伴随的低穿透性和低功率会限制太赫兹调频连续波成像系统的应用场景。因此,聚焦于太赫兹波无损检测领域,提出一种时分频分复用的114～500 GHz超宽带太赫兹信号的产生方式,基于多频段共孔径准光设计,实现超带宽信号的共孔径,频率可扩展至1.1 THz。提出一种频段融合算法,实现了超宽带信号的有效融合,距离分辨力提升至460μm,通过人工设计的多层复合材料验证了系统及算法的有效性,并得到封装集成电路(IC)芯片的高分辨三维成像结果。     

宽带太赫兹偶极子光电导接收天线研究

太赫兹光电导天线广泛应用于宽带脉冲太赫兹波的检测,是太赫兹光谱和成像系统中的重要器件。偶极子光电导天线由于其结构简单、制作容易成为使用最广泛的一类太赫兹光电导接收天线。衡量太赫兹光电导探测天线的一个重要指标是其响应带宽。针对偶极子天线的探测带宽,分别对天线臂长为10、50、150 m的偶极子天线及一种作为对比的178 m的蝶形天线（Bowtie antenna）进行了实验及理论研究。结果显示其探测带宽随天线臂长增加而减小,与微波天线理论一致。进一步的,采用商用电磁场数值仿真软件进行建模仿真,仿真结果与理论及实验结果具有很好的一致性,证实数值仿真已在很大程度上模拟出实际天线的特性,从而为优化结构参数制作大宽带和高灵敏度的太赫兹天线提供支持。同时,对超半球硅衬底透镜对天线接收频谱的影响也进行了探讨。     

光子辅助的宽带太赫兹通信技术

首先,介绍了光子辅助的宽带太赫兹通信系统中的关键技术.然后,介绍了大容量和长距离太赫兹无线和有线通信技术方面的研究进展.采用这些关键技术,先后实现了太赫兹信号超过1 Tbit/s的无线传输,以及超过100 Gbit/s太赫兹信号在无太赫兹放大器的情况下无线传输54.6 m.最后,介绍了采用空芯光纤进行有线传输超过100...     

智能反射面与太赫兹通信协同应用探讨

太赫兹通信是为6G无线通信网络提供足够带宽和实现超高数据速率的一种前沿技术,智能反射面是为了缓解太赫兹波段的无线传输脆弱性,通过调整无源反射元件的相位偏移,提高频谱效率、增强覆盖能力的技术。介绍了智能反射面赋能太赫兹通信的关键技术,展望了智能反射面在6G通信网络中的应用方向和面临的挑战。     

激光偏振态对光纤型太赫兹时域光谱仪的影响

采用光纤飞秒激光器与光纤耦合型太赫兹光电导天线相结合的方案,设计并研制了光纤型太赫兹时域光谱系统。通过实验研究了激光偏振态对太赫兹时域波形、强度以及光谱特性的影响,通过对飞秒激光偏振态的精确控制与优化,消除了时域脉冲分裂现象,获得了高信噪比的单脉冲太赫兹时域波形。     

新型太赫兹光子晶体OAM光纤设计

太赫兹通信兼具微波通信和光波通信的优势,是解决通信容量紧缺难题的最有效技术手段之一。针对太赫兹波段吸收损耗严重及抗外在扰动差,难以支持长距传输问题,设计了一种基于环形光子晶体光纤(PCF)结构的新型太赫兹光纤。以现有常见材料作为光纤基底材质,通过创新光纤结构中空气孔排布方式,抵消材料高吸收损耗,以支持高性能轨道角动量(OAM)模式传输。选择最优参数,实现6个OAM模式群的高模式质量、低限制损耗和宽带宽的稳定传输。在0.2~0.9 THz宽波段内,实现模式纯度超过88.9%,限制损耗小于10^-7 dB/m。通过软件仿真实验设计,解决了太赫兹与OAM技术相结合的关键问题,为模分复用(MDM)技术在太赫兹通信系统的应用奠定了理论研究基础。     

基于频率梳的太赫兹辐射强度测量

为实现太赫兹辐射特性精准认知,开展太赫兹辐射绝对强度测量研究。通过光学频率梳产生太赫兹频率梳,利用太赫兹频率梳实现太赫兹辐射源空间强度测量。本文利用电光采样和光电导探测两种方式,实现了100 GHz辐射源空间辐射强度测量;将100 GHz辐射总功率溯源到标准太赫兹功率计,实现太赫兹辐射强度绝对测量。分析比较了利用800 nm空间光进行电光采样和利用1550 nm光纤激光进行光电导探测的测量结果。本文在不同距离下,对太赫兹辐射源的空间辐射绝对强度进行了测量,实验揭示了太赫兹辐射传输的空间演化特性。     

高灵敏度低噪声太赫兹电光探测器研究

本文选用相同光电响应灵敏度的高性能PIN光电二极管,将探测激光信号转换为电流信号,再通过低噪声电流-电压转换将电流信号转换为电压信号,通过采用具有很强共模信号抑制能力的差分放大器,不仅极大地抑制了太赫兹信号本身携带的噪声,也避免了探测激光强度扰动引起的测量误差.差分最后经过带通滤波器控制工作带宽和进行降噪处理,经由主放大器实现太赫兹信号输出.实验表明,该探测器具有高灵敏度、高信噪比、宽工作带宽等显著特点,完全满足了太赫兹时域光谱系统研究的需要.     

新型光控砷化镓/侧边抛磨太赫兹光纤调制器

太赫兹调制器作为太赫兹技术应用的重要器件之一，在太赫兹通信、成像和传感等领域具有广泛应用前景。但是目前太赫兹调制器调制深度、工作带宽、稳定性等有待提升，这制约了太赫兹技术的进一步推广与发展。基于此，设计并制备了一种新型光控砷化镓/侧边抛磨太赫兹光纤（SPTF）调制器，将砷化镓转移到太赫兹光纤抛磨区，增强太赫兹波倏逝场与砷化镓相互作用。在外置808 nm激光器照射下实现对太赫兹波幅度调制，调制深度达到97.4%。实验结果表明，这种新型的光纤调制器具有较好的光控调制效果。同时，该器件体积小、集成度高，具有广泛应用的潜力。     

Broadband arbitrary waveform generation based on microwave frequency upshifting in optical fibers

An interesting method for broadband arbitrary waveform generation is based on the frequency upshifting of a narrowband microwave signal. In this technique, the original microwave signal is imaged into a temporally compressed replica using a simple and practical fiber-based system. Recently, it has been shown that the conventional limitations of this approach (e.g., bandwidth limitations) can be overcome by exploiting a temporal self-imaging (Talbot) effect in fiber. This effect can be used whenever the signal to be imaged is a quasi-periodic waveform (e.g., microwave tones or any arbitrary periodic waveform). This paper provides a comprehensive study of the microwave frequency upshifting technique with special focus on the Talbot-based approach. Following a theoretical analysis of the design constraints of the conventional approach, the Talbot-based solution is theoretically investigated in detail. In particular, the design specifications of a Talbot-based microwave upshifting system are derived, and the practical capabilities and constraints of these systems (e.g., in terms of achievable bandwidth) are stated and examined. The theoretical findings are confirmed by means of numerical simulations. Moreover, a numerical study of the influence of higher-order (second-order) dispersion terms on system performance is presented, and some additional design rules to minimize the associated detrimental effects are given. The results show that microwave frequencies up to a few hundreds of gigahertz over nanosecond temporal windows can be easily obtained with the described technique using input optical bandwidths in the terahertz range. This has been experimentally confirmed.     

Photonic Generation of Ultrawideband Signals

Ultrawideband (UWB) that is regulated by the Federal Communications Commission (FCC) for short-range high-throughput wireless communication and sensor networks with advantageous features, such as immunity to multipath fading, extremely short time duration, being carrier free, and having low duty cycle, wide bandwidth, and low power spectral density, has been a topic of interest recently. By wireless transmission, UWB communications systems can only operate in a short distance of a few meters to tens of meters. The convergence of UWB and optical fiber distribution techniques, or UWB over fiber, offers the availability of undisrupted service across different networks and eventually achieves high-data-rate access at any time and from any place. To distribute the UWB signals over the optical fiber, it is also desirable that the UWB signals can be generated in the optical domain without having extra electrical-to-optical conversion. In addition, UWB signals that are generated in the optical domain can be easily tailored to have a spectrum that meets the FCC-specified spectral mask. In this paper, techniques to generate UWB signals in the optical domain will be discussed. These techniques are divided into three categories, with the generation of UWB signals based on the following: 1) phase-modulation-to-intensity-modulation conversion; 2) a photonic microwave delay-line filter; and 3) optical spectral shaping and dispersion-induced frequency-to-time mapping. The areas for future development and the challenge of implementation of these techniques for practical applications will also be discussed.     

石墨烯太赫兹调制器及330 GHz无线通信系统

现有太赫兹无线通信系统通常采用微波倍频或直接调源的方式。本文从太赫兹波空间调制技术出发,研究了一种基于直接调制技术的太赫兹无线通信系统。重点探索了一种基于石墨烯/半导体硅的复合结构(GOS),研究出调制速率达到1 MHz,调制深度50%以上,工作频带覆盖0.2 THz~2 THz频段的新型全光学太赫兹调制器。在此基础上,构建了330 GHz载波频率的太赫兹无线通信系统,实现了1 Mbps的通信速率。     

In-House Networks Using Multimode Polymer Optical Fiber for Broadband Wireless Services

A novel system concept is presented to transport microwave signals over an in-house multimode graded-index polymer optical fiber network, in order to feed the radio access points in high-capacity wireless LANs. By employing optical frequency multiplying, the network's intrinsically limited bandwidth is overcome. The feasibility of this concept to carry data at several hundreds of Mbit/s speed for various microwave signal formats at carrier frequencies in the tens of GHz range is shown. The concept enables cost-effective system implementation, and easy upgrading by offering data signal transparency. It can readily be integrated with other system technologies such as wired Gigabit Ethernet in a single multi-service in-house polymer optical fiber network.     

太赫兹雷达技术

太赫兹雷达具有带宽大、分辨率高、多普勒敏感、抗干扰等独特优势,是目标探测领域的重要发展方向。该文首先回顾和介绍了电子学和光学太赫兹雷达系统历史、现状和最新进展,其次对太赫兹雷达目标特性从机理、计算、测量3个方面进行了梳理和概要介绍,同时阐述了太赫兹ISAR、SAR、阵列和孔径编码成像研究状况,简要介绍了太赫兹雷达在预警探测、安检反恐等领域的应用,最后对太赫兹雷达技术的发展方向进行了展望。      

太赫兹波段反谐振光纤偏振分束器设计

偏振分束器是在光传感和集成光学等领域中非常重要的光学元器件,太赫兹波段被认为是未来大容量无线通信的载体.而双芯空芯反谐振光纤结构设计更加多变,对包层结构没有严格要求,能实现较高的性能以满足人们更多样化的需求,以双芯空芯反谐振光纤为基础设计适用于太赫兹波段的偏振分束器越来越值得深入研究.提出一种以环烯烃聚合物为基底材料的...     

Co‐simulation‐based modeling and performance analysis of hybrid fiber–wireless links

We present a new approach for the performance analysis of hybrid fiber/wireless communication systems. This approach is based on a co‐simulation using two types of dedicated software: the first is used for RF/wireless systems whereas the second is devoted to optical communication systems. The proposed method enables simultaneous simulation of all elements of the radio‐over‐fiber link with accurate modeling. A low‐cost wireless local area network over a fiber distribution system is implemented in order to validate the results experimentally. Simulation results are in good agreement with experimental measurements in terms of EVM evolution for different link element configurations. Copyright © 2011 John Wiley & Sons, Ltd.     

大功率速调管的技术现状和最新进展

大功率速调管是一种基于速度调制原理将电子注能量转换成微波能量的微波真空电子器件,它具有高功率、高效率、高增益和高稳定性等优点,是微波真空电子器件中脉冲功率和平均功率最高的器件。速调管自20世纪30年代发明以来,在粒子加速器、雷达和通信等微波电子系统,以及真空电子技术进步的推动下,已发展成功多种类型大功率速调管,其频率覆盖整个微波,并扩展到毫米波和太赫兹波段,最大脉冲功率达200MW,最大平均(连续波)功率达MW级。近年来,在高能粒子加速器、宽带雷达系统、毫米波和太赫兹波电子系统的推动下,大功率速调管取得了令人瞩目的进步,本文比较系统地介绍了大功率速调管的技术现状和在提高功率、提高效率、提高工作频率、展宽带宽等方面取得的最新进展。