Nondestructive evaluation is one of the key envisaged applications for terahertz technology due to nonionizing energy levels and the ability to penetrate many optically opaque materials. Conventional terahertz imaging systems typically rely on raster scanning the target with a moving transceiver, or make use of goniometric beam manipulation schemes. As an alternative, we propose the use of a Risley-prism, essentially a cascaded pair of independently rotating prisms, to function as a simple beam-steering mechanism. When deployed in conjunction with an aspheric, telecentric objective, the Risley-prism allows for scanning a focused terahertz beam in two dimensions. We utilize 3D-printed cyclic olefin copolymer, a low-loss and low-dispersion polymer, to minimize material loss and facilitate the construction of these bulk optics. Owing to true time delay, our imaging system operates over 220–330 GHz, making use of this bandwidth for resolving depth features and hidden objects. We achieve a spatial resolution of 0.419 lp/mm over a circular scanning region 27.8 mm in diameter. The proposed Risley-prism imaging system offers a simple solution to the complicated problem of broadband and high resolution imaging, and hence, is readily amenable to widespread adoption and commercial applications.
{"title":"Terahertz Imaging With 3D-Printed Risley-Prism and Telecentric Objective","authors":"Bryce Chung;Daniel Headland;Withawat Withayachumnankul","doi":"10.1109/TTHZ.2024.3404642","DOIUrl":"https://doi.org/10.1109/TTHZ.2024.3404642","url":null,"abstract":"Nondestructive evaluation is one of the key envisaged applications for terahertz technology due to nonionizing energy levels and the ability to penetrate many optically opaque materials. Conventional terahertz imaging systems typically rely on raster scanning the target with a moving transceiver, or make use of goniometric beam manipulation schemes. As an alternative, we propose the use of a Risley-prism, essentially a cascaded pair of independently rotating prisms, to function as a simple beam-steering mechanism. When deployed in conjunction with an aspheric, telecentric objective, the Risley-prism allows for scanning a focused terahertz beam in two dimensions. We utilize 3D-printed cyclic olefin copolymer, a low-loss and low-dispersion polymer, to minimize material loss and facilitate the construction of these bulk optics. Owing to true time delay, our imaging system operates over 220–330 GHz, making use of this bandwidth for resolving depth features and hidden objects. We achieve a spatial resolution of 0.419 lp/mm over a circular scanning region 27.8 mm in diameter. The proposed Risley-prism imaging system offers a simple solution to the complicated problem of broadband and high resolution imaging, and hence, is readily amenable to widespread adoption and commercial applications.","PeriodicalId":13258,"journal":{"name":"IEEE Transactions on Terahertz Science and Technology","volume":"14 4","pages":"446-454"},"PeriodicalIF":3.9,"publicationDate":"2024-03-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141494984","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In this article, the propagation loss of 0.14 THz signal propagating for 27 km at sea is measured experimentally and compared with the simulation results of model in the International Telecommunication Union-Radiocommunication Sector. The results show that the average difference between the simulated and experimental values of signal received power is −5.2 dB, and all the simulation results overestimate the propagation loss. Considering that evaporation duct is ubiquitous in the marine atmosphere and may affect the propagation characteristics of terahertz wave, a new computational model is proposed. More than half of the simulated values based on this model agree well with the measured data, with an average difference of −1.3 dB, but the maximum difference of a single point reaches −18.6 dB, which is mainly caused by the sensitivity of the model to meteorological parameters. The “waveguide effect” in the evaporation duct environment is further simulated by adjusting the transmit antenna height from 29 to 10 m. At this time, although the atmospheric absorption loss increases by 1 dB on average, the total path loss decreases by 5.4 dB on average, which effectively reduces the propagation loss and makes it possible for the long-range transmission of terahertz wave.
{"title":"Modeling Analysis and Research of Terahertz Wave Propagation Experiment at Sea","authors":"Xiangchun Cao;Juan Liu;Jianhong Hao;Qiang Zhao;Bixi Xue;Fang Zhang;Jieqing Fan;Changxing Lin;Zhiwei Dong","doi":"10.1109/TTHZ.2024.3379749","DOIUrl":"https://doi.org/10.1109/TTHZ.2024.3379749","url":null,"abstract":"In this article, the propagation loss of 0.14 THz signal propagating for 27 km at sea is measured experimentally and compared with the simulation results of model in the International Telecommunication Union-Radiocommunication Sector. The results show that the average difference between the simulated and experimental values of signal received power is −5.2 dB, and all the simulation results overestimate the propagation loss. Considering that evaporation duct is ubiquitous in the marine atmosphere and may affect the propagation characteristics of terahertz wave, a new computational model is proposed. More than half of the simulated values based on this model agree well with the measured data, with an average difference of −1.3 dB, but the maximum difference of a single point reaches −18.6 dB, which is mainly caused by the sensitivity of the model to meteorological parameters. The “waveguide effect” in the evaporation duct environment is further simulated by adjusting the transmit antenna height from 29 to 10 m. At this time, although the atmospheric absorption loss increases by 1 dB on average, the total path loss decreases by 5.4 dB on average, which effectively reduces the propagation loss and makes it possible for the long-range transmission of terahertz wave.","PeriodicalId":13258,"journal":{"name":"IEEE Transactions on Terahertz Science and Technology","volume":"14 3","pages":"377-385"},"PeriodicalIF":3.2,"publicationDate":"2024-03-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140820386","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Compared to the traditional Volterra nonlinear equalizer (VNE), the multi-input, multioutput (MIMO)–VNE is capable of addressing the signal degradation caused by higher order cross-talk. Naturally, the gains from the MIMO architecture are at the cost of doubling the amount of computation. To reduce the calculation workload, based on the two-stage serial–parallel MIMO architecture, the absolute operation of the cross-beating terms and the pruning technique, an extremely low-complexity MIMO–VNE, namely absolute-term pruned two-stage (AT-P-2S) MIMO–VNE, has been proposed in this article. With the proposed AT-P-2S MIMO–VNE and optical mixing technique, terahertz wave transmission over 500 GHz is successfully demonstrated. The experimental results show that the AT–P–2S–MIMO–VNE demonstrates very comparable BER performance to the MIMO–VNE, and can achieve more than 4% capacity improvement in the beyond-500 GHz band. Meanwhile, in contrast to MIMO–VNE, AT–P–2S–MIMO–VNE can reduce the equalizer real multiplication operation by more than 94%. By striking a balance between performance and complexity, the proposed AT–P–2S–MIMO–VNE offers an appealing solution to enhance the efficiency and effectiveness of future communication systems.
{"title":"Beyond 500 GHz THz Wireless Links Based on Heterodyne Photomixing and Absolute Operation Pruned Two-Stage MIMO–Volterra","authors":"Junting Shi;Yanyi Wang;Jiao Zhang;Xianming Zhao;Min Zhu;Wen Zhou;Jianjun Yu","doi":"10.1109/TTHZ.2024.3377354","DOIUrl":"https://doi.org/10.1109/TTHZ.2024.3377354","url":null,"abstract":"Compared to the traditional Volterra nonlinear equalizer (VNE), the multi-input, multioutput (MIMO)–VNE is capable of addressing the signal degradation caused by higher order cross-talk. Naturally, the gains from the MIMO architecture are at the cost of doubling the amount of computation. To reduce the calculation workload, based on the two-stage serial–parallel MIMO architecture, the absolute operation of the cross-beating terms and the pruning technique, an extremely low-complexity MIMO–VNE, namely absolute-term pruned two-stage (AT-P-2S) MIMO–VNE, has been proposed in this article. With the proposed AT-P-2S MIMO–VNE and optical mixing technique, terahertz wave transmission over 500 GHz is successfully demonstrated. The experimental results show that the AT–P–2S–MIMO–VNE demonstrates very comparable BER performance to the MIMO–VNE, and can achieve more than 4% capacity improvement in the beyond-500 GHz band. Meanwhile, in contrast to MIMO–VNE, AT–P–2S–MIMO–VNE can reduce the equalizer real multiplication operation by more than 94%. By striking a balance between performance and complexity, the proposed AT–P–2S–MIMO–VNE offers an appealing solution to enhance the efficiency and effectiveness of future communication systems.","PeriodicalId":13258,"journal":{"name":"IEEE Transactions on Terahertz Science and Technology","volume":"14 3","pages":"364-376"},"PeriodicalIF":3.2,"publicationDate":"2024-03-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140820347","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-03-14DOI: 10.1109/TTHZ.2024.3401041
Yiran Cui;Georgios C. Trichopoulos
In this article, we show how active terahertz (THz) imaging systems can exploit the unique propagation properties of THz waves to reconstruct images of nonline-of-sight (NLoS) scenes. Most building surfaces' material properties and roughness allow for a unique combination of diffuse and strong specular scattering. As a result, most surfaces behave as lossy mirrors that enable propagation paths between a THz camera and the NLoS scenes. We propose a mirror folding algorithm that tracks the multireflection propagation of THz waves to correct the image from cluttering and see around occlusions without prior knowledge of the scene geometry and material properties. To validate the feasibility of the proposed NLoS imaging approach, we carried out a numerical analysis and developed two THz imaging systems to demonstrate real-world NLoS imaging experiments in sub-THz bands (270–300 GHz). The results show the capability of THz radar imaging systems to recover both the geometry and pose of LoS and NLoS objects with centimeter-scale resolution in various multipath propagation scenarios. THz NLoS imaging can operate in low visibility conditions (e.g., night, strong ambient light, and smoke) and uses computationally inexpensive image reconstruction algorithms.
在本文中，我们展示了主动式太赫兹（THz）成像系统如何利用太赫兹波的独特传播特性来重建非视线（NLoS）场景的图像。大多数建筑表面的材料特性和粗糙度允许漫散射和强镜面散射的独特组合。因此，大多数表面就像一面有损的镜子，使太赫兹相机和非视线场景之间有了传播路径。我们提出了一种镜面折叠算法，该算法可跟踪太赫兹波的多反射传播，以校正杂波图像，并在不事先了解场景几何和材料属性的情况下看到遮挡物周围的情况。为了验证所提出的无损成像方法的可行性，我们进行了数值分析，并开发了两个太赫兹成像系统，以演示真实世界中的次太赫兹频段（270-300 GHz）无损成像实验。结果表明，在各种多径传播情况下，太赫兹雷达成像系统都能以厘米级的分辨率恢复 LoS 和 NLoS 物体的几何形状和姿态。太赫兹 NLoS 成像可在低能见度条件下（如夜间、强环境光和烟雾）运行，并使用计算成本低廉的图像重建算法。
{"title":"Seeing Around Obstacles Using Active Terahertz Imaging","authors":"Yiran Cui;Georgios C. Trichopoulos","doi":"10.1109/TTHZ.2024.3401041","DOIUrl":"https://doi.org/10.1109/TTHZ.2024.3401041","url":null,"abstract":"In this article, we show how active terahertz (THz) imaging systems can exploit the unique propagation properties of THz waves to reconstruct images of nonline-of-sight (NLoS) scenes. Most building surfaces' material properties and roughness allow for a unique combination of diffuse and strong specular scattering. As a result, most surfaces behave as lossy mirrors that enable propagation paths between a THz camera and the NLoS scenes. We propose a mirror folding algorithm that tracks the multireflection propagation of THz waves to correct the image from cluttering and see around occlusions without prior knowledge of the scene geometry and material properties. To validate the feasibility of the proposed NLoS imaging approach, we carried out a numerical analysis and developed two THz imaging systems to demonstrate real-world NLoS imaging experiments in sub-THz bands (270–300 GHz). The results show the capability of THz radar imaging systems to recover both the geometry and pose of LoS and NLoS objects with centimeter-scale resolution in various multipath propagation scenarios. THz NLoS imaging can operate in low visibility conditions (e.g., night, strong ambient light, and smoke) and uses computationally inexpensive image reconstruction algorithms.","PeriodicalId":13258,"journal":{"name":"IEEE Transactions on Terahertz Science and Technology","volume":"14 4","pages":"433-445"},"PeriodicalIF":3.9,"publicationDate":"2024-03-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141495181","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-03-05DOI: 10.1109/TTHZ.2024.3373251
Xianfei Chen;Houxiu Xiao;Yu Huang;Runfeng Tang;Donghui Xia;Xiaotao Han
The misalignment is an important factor that accounts for the deviation of the experimental results from the theoretical design of high-frequency gyrotrons. This article investigates the effect of the electron beam misalignment on the operation of a second harmonic 0.8 THz gyrotron through theoretical analysis and experiments. The rise of the starting current, efficiency degradation, continuous frequency tunability, and harmonic mode competition of the 0.8 THz gyrotron under the effect of different types of beam misalignment is analyzed comprehensively using a self-consistent model, providing a general picture for the potential effect of beam misalignment on high-frequency harmonic gyrotrons. The alignment process and experimental results of the 0.8 THz gyrotron tube installed in a 15 T magnet with XY -tables and optical probes are also discussed. The results are referential to the development of high-frequency gyrotrons for high-power THz applications.
{"title":"Theoretical and Experimental Investigation on the Effect of Beam Misalignment on a Second Harmonic 0.8 THz Gyrotron","authors":"Xianfei Chen;Houxiu Xiao;Yu Huang;Runfeng Tang;Donghui Xia;Xiaotao Han","doi":"10.1109/TTHZ.2024.3373251","DOIUrl":"https://doi.org/10.1109/TTHZ.2024.3373251","url":null,"abstract":"The misalignment is an important factor that accounts for the deviation of the experimental results from the theoretical design of high-frequency gyrotrons. This article investigates the effect of the electron beam misalignment on the operation of a second harmonic 0.8 THz gyrotron through theoretical analysis and experiments. The rise of the starting current, efficiency degradation, continuous frequency tunability, and harmonic mode competition of the 0.8 THz gyrotron under the effect of different types of beam misalignment is analyzed comprehensively using a self-consistent model, providing a general picture for the potential effect of beam misalignment on high-frequency harmonic gyrotrons. The alignment process and experimental results of the 0.8 THz gyrotron tube installed in a 15 T magnet with \u0000<italic>XY</i>\u0000-tables and optical probes are also discussed. The results are referential to the development of high-frequency gyrotrons for high-power THz applications.","PeriodicalId":13258,"journal":{"name":"IEEE Transactions on Terahertz Science and Technology","volume":"14 3","pages":"395-403"},"PeriodicalIF":3.2,"publicationDate":"2024-03-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140820385","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-03-04DOI: 10.1109/TTHZ.2024.3368955
{"title":"IEEE Transactions on Terahertz Science and Technology Publication Information","authors":"","doi":"10.1109/TTHZ.2024.3368955","DOIUrl":"https://doi.org/10.1109/TTHZ.2024.3368955","url":null,"abstract":"","PeriodicalId":13258,"journal":{"name":"IEEE Transactions on Terahertz Science and Technology","volume":"14 2","pages":"C3-C3"},"PeriodicalIF":3.2,"publicationDate":"2024-03-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=10459092","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140031717","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-03-04DOI: 10.1109/TTHZ.2024.3368966
{"title":"TechRxiv: Share Your Preprint Research with the World!","authors":"","doi":"10.1109/TTHZ.2024.3368966","DOIUrl":"https://doi.org/10.1109/TTHZ.2024.3368966","url":null,"abstract":"","PeriodicalId":13258,"journal":{"name":"IEEE Transactions on Terahertz Science and Technology","volume":"14 2","pages":"300-300"},"PeriodicalIF":3.2,"publicationDate":"2024-03-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=10459071","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140031687","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-03-04DOI: 10.1109/TTHZ.2024.3368953
{"title":"IEEE Transactions on Terahertz Science and Technology Information for Authors","authors":"","doi":"10.1109/TTHZ.2024.3368953","DOIUrl":"https://doi.org/10.1109/TTHZ.2024.3368953","url":null,"abstract":"","PeriodicalId":13258,"journal":{"name":"IEEE Transactions on Terahertz Science and Technology","volume":"14 2","pages":"298-299"},"PeriodicalIF":3.2,"publicationDate":"2024-03-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=10459098","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140031663","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-03-04DOI: 10.1109/TTHZ.2024.3368951
{"title":"IEEE Microwave Theory and Techniques Society Information","authors":"","doi":"10.1109/TTHZ.2024.3368951","DOIUrl":"https://doi.org/10.1109/TTHZ.2024.3368951","url":null,"abstract":"","PeriodicalId":13258,"journal":{"name":"IEEE Transactions on Terahertz Science and Technology","volume":"14 2","pages":"C2-C2"},"PeriodicalIF":3.2,"publicationDate":"2024-03-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=10459104","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140031722","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-03-02DOI: 10.1109/TTHZ.2024.3393789
{"title":"TechRxiv: Share Your Preprint Research with the World!","authors":"","doi":"10.1109/TTHZ.2024.3393789","DOIUrl":"https://doi.org/10.1109/TTHZ.2024.3393789","url":null,"abstract":"","PeriodicalId":13258,"journal":{"name":"IEEE Transactions on Terahertz Science and Technology","volume":"14 3","pages":"430-430"},"PeriodicalIF":3.2,"publicationDate":"2024-03-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=10517801","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140820382","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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