Broadband Terahertz Devices and Communication Technologies

A special issue of Micromachines (ISSN 2072-666X). This special issue belongs to the section "E:Engineering and Technology".

Deadline for manuscript submissions: closed (10 April 2023) | Viewed by 26779

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Special Issue Editors

College of Information Science and Electronic Engineering, Zhejiang University, Hangzhou 310027, China
Interests: broadband THz communications; ultra-fast fiber-optical communications; advanced signal processing; THz sensing
Special Issues, Collections and Topics in MDPI journals
Department of Applied Physics, KTH Royal Institute of Technology, 114 19 Stockholm, Sweden
Interests: free-space communications; terahertz photonics; high-speed data transmissions
Special Issues, Collections and Topics in MDPI journals
Institute of Microelectronics, Agency for Science, Technology and Research, Singapore 138634, Singapore
Interests: THz metadevices; THz photonic integrated circuits

Special Issue Information

Dear Colleagues,

The remarkable explosion of wireless devices and bandwidth-consuming Internet applications has boosted the demand for ultra-high data rate wireless communications. The wireless traffic volume is foreseen to be sufficient to match or even surpass wired services by 2030, and the high-precision wireless services will need to be guaranteed with a peak data rate of well beyond 100 Gbit/s, eventually 1 Tbit/s. To meet the exponentially increasing traffic demand, new regions in the radio spectrum are explored. The terahertz band (0.1 THz-10 THz), sandwiched between microwave frequencies and optical frequencies, is considered as a next breakthrough-point to revolutionize the communication technology attributed to its rich spectrum resources. It is recognized as a promising candidate for future rate-greedy applications, such as 6G communications. In the World Radio Communication Conferences 2019, the identification of frequency bands in the frequency range 275 GHz–450 GHz is permitted for the use of land-mobile and fixed services applications, indicating the potential standardization of the low-frequency window of the terahertz band for near-future wireless communications.

Motivated by the potential of the terahertz wireless communications, this Special Issue seeks critical technology breakthroughs in terms of the terahertz communications. The Special Issue topics include, but are not limited to, broadband terahertz devices, terahertz frontend and antenna design, baseband processing for THz links, terahertz propagation and channel modelling, system-level demonstration of terahertz communications.

Dr. Lu Zhang
Dr. Xiaodan Pang
Dr. Prakash Pitchappa
Guest Editors

Manuscript Submission Information

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Keywords

  • THz source (electrical, photonic)
  • THz mixer (electrical, photonic)
  • THz modulator (electrical, photonic)
  • THz amplifier (low-noise, power, etc.)
  • passive THz devices (filter, polarizer, antenna, etc.)
  • THz frontend (electrical, photonic)
  • baseband processing for THz links (transmitter, receiver)
  • terahertz propagation and channel modelling
  • system-level demonstration of electrical terahertz communications
  • system-level demonstration of photonic terahertz communications

Published Papers (12 papers)

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Editorial

Jump to: Research, Review

3 pages, 182 KiB  
Editorial
Editorial for the Special Issue on Broadband Terahertz Devices and Communication Technologies
by Lu Zhang, Xiaodan Pang and Prakash Pitchappa
Micromachines 2023, 14(5), 1044; https://0-doi-org.brum.beds.ac.uk/10.3390/mi14051044 - 12 May 2023
Cited by 1 | Viewed by 703
Abstract
The remarkable explosion of wireless devices and bandwidth-consuming Internet applications have boosted the demand for wireless communications with ultra-high data rate [...] Full article
(This article belongs to the Special Issue Broadband Terahertz Devices and Communication Technologies)

Research

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12 pages, 3578 KiB  
Article
Room-Temperature CMOS Monolithic Resonant Triple-Band Terahertz Thermal Detector
by Xu Wang, Ting-Peng Li, Shu-Xia Yan and Jian Wang
Micromachines 2023, 14(3), 627; https://0-doi-org.brum.beds.ac.uk/10.3390/mi14030627 - 09 Mar 2023
Cited by 1 | Viewed by 1037
Abstract
Multiband terahertz (THz) detectors show great application potential in imaging, spectroscopy, and sensing fields. Thermal detectors have become a promising choice because they could sense THz radiations on the whole spectrum. This paper demonstrates the operation principle, module designs with in-depth theoretical analysis, [...] Read more.
Multiband terahertz (THz) detectors show great application potential in imaging, spectroscopy, and sensing fields. Thermal detectors have become a promising choice because they could sense THz radiations on the whole spectrum. This paper demonstrates the operation principle, module designs with in-depth theoretical analysis, and experimental validation of a room-temperature CMOS monolithic resonant triple-band THz thermal detector. The detector, which consists of a compact triple-band octagonal ring antenna and a sensitive proportional to absolute temperature (PTAT) sensor, has virtues of room-temperature operation, low cost, easy integration, and mass production. Good experimental results are obtained at 0.91 THz, 2.58 THz, and 4.2 THz with maximum responsivities of 32.6 V/W, 43.2 V/W, and 40 V/W, respectively, as well as NEPs of 1.28 μW/Hz0.5, 2.19 μW/Hz0.5, and 2.37 μW/Hz0.5, respectively, providing great potential for multiband THz sensing and imaging systems. Full article
(This article belongs to the Special Issue Broadband Terahertz Devices and Communication Technologies)
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15 pages, 5448 KiB  
Article
Design of a Differential Low-Noise Amplifier Using the JFET IF3602 to Improve TEM Receiver
by Shengjie Wang, Yuqi Zhao, Yishu Sun, Weicheng Wang, Jian Chen and Yang Zhang
Micromachines 2022, 13(12), 2211; https://0-doi-org.brum.beds.ac.uk/10.3390/mi13122211 - 13 Dec 2022
Cited by 3 | Viewed by 2544
Abstract
The observed data of transient electromagnetic (TEM) systems is often contaminated by various noises. Even after stacking averages or applying various denoising algorithms, the interference of the system noise floor cannot be eliminated fundamentally, which limits the survey capability and detection efficiency of [...] Read more.
The observed data of transient electromagnetic (TEM) systems is often contaminated by various noises. Even after stacking averages or applying various denoising algorithms, the interference of the system noise floor cannot be eliminated fundamentally, which limits the survey capability and detection efficiency of TEM. To improve the noise performance of the TEM receiver, we have designed a low-noise amplifier using the current source long-tail differential structure and JFET IF3602 through analyzing the power spectrum characteristics of the TEM forward response. By the designed circuit structure, the JFET operating point is easy to set up. The adverse effect on the JFET differential structure by JFET performance differences is also weakened. After establishing the noise model and optimizing the parameters, the designed low-noise differential amplifier has a noise level of 0.60nV/Hz, which increases the number of effective data 2.6 times compared with the LT1028 amplifier. Full article
(This article belongs to the Special Issue Broadband Terahertz Devices and Communication Technologies)
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11 pages, 4873 KiB  
Article
Compact Wideband Four-Port MIMO Antenna for Sub-6 GHz and Internet of Things Applications
by Nathirulla Sheriff, Sharul Kamal, Hassan Tariq Chattha, Tan Kim Geok and Bilal A. Khawaja
Micromachines 2022, 13(12), 2202; https://0-doi-org.brum.beds.ac.uk/10.3390/mi13122202 - 12 Dec 2022
Cited by 4 | Viewed by 1550
Abstract
A compact four-port multi-input, multi-output (MIMO) antenna with good isolation is proposed for sub-6 GHz and Internet of Things (IoT) applications. Four similar L-shaped antennae are placed orthogonally at 7.6 mm distance from the corner of the FR4 substrate. The wideband characteristics and [...] Read more.
A compact four-port multi-input, multi-output (MIMO) antenna with good isolation is proposed for sub-6 GHz and Internet of Things (IoT) applications. Four similar L-shaped antennae are placed orthogonally at 7.6 mm distance from the corner of the FR4 substrate. The wideband characteristics and the required frequency band are achieved through the L-shaped structure and with proper placement of the slots on the substrate. To obtain good isolation between the ports, rectangular slots are etched in the bottom layer and are interconnected. The proposed antenna has total dimensions of 40 mm × 40 mm × 1.6 mm. The interconnected ground plane provides good isolation of less than −17 dB between the ports, and the impedance bandwidth obtained by the proposed four-port antenna is about 54% between the frequency range of 3.2 GHz to 5.6 GHz, thus providing a wideband antenna characteristic covering sub-6 GHz 5G bands (from 3.4 to 3.6 GHz and 4.8 to 5 GHz) and the WLAN band (5.2 GHz). The proposed design antenna is fabricated and tested. Good experimental results are achieved when compared with the simulation results. As the proposed design is compact and low profile, this antenna could be a suitable candidate for 5G and IoT devices. Full article
(This article belongs to the Special Issue Broadband Terahertz Devices and Communication Technologies)
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12 pages, 4971 KiB  
Article
A G-Band Broadband Continuous Wave Traveling Wave Tube for Wireless Communications
by Yuan Feng, Xingwang Bian, Bowen Song, Ying Li, Pan Pan and Jinjun Feng
Micromachines 2022, 13(10), 1635; https://0-doi-org.brum.beds.ac.uk/10.3390/mi13101635 - 29 Sep 2022
Cited by 5 | Viewed by 1622
Abstract
Development of a G-band broadband continuous wave (CW) traveling wave tube (TWT) for wireless communications is described in this paper. This device provides the saturation output power over 8 W and the saturation gain over 30.5 dB with a bandwidth of 27 GHz. [...] Read more.
Development of a G-band broadband continuous wave (CW) traveling wave tube (TWT) for wireless communications is described in this paper. This device provides the saturation output power over 8 W and the saturation gain over 30.5 dB with a bandwidth of 27 GHz. The maximum output power is 16 W and the bandwidth of 10 W output power is 23 GHz. The 3 dB bandwidth is greater than 12.3% of fc (center frequency). The gain ripple is less than 10 dB in band. A pencil beam of 50 mA and 20 kV is used and a transmission ratio over 93% is realized. The intercept power of the beam is less than 70 W and the TWT is conduction cooled through mounting plate and air fan, which makes the device capable of operating in continuous wave mode. A Pierce’s electron gun and periodic permanent magnets are employed. Chemical vapor deposition diamond disc is used in the input and output radio frequency (RF) windows to minimize the loss and voltage standing wave ratios of the traveling wave tube. Double stages deeply depressed collector is used for improving the total efficiency of the device, which can be over 5.5% in band. The weight of the device is 2.5 kg, and the packaged size is 330 mm × 70 mm × 70 mm. Full article
(This article belongs to the Special Issue Broadband Terahertz Devices and Communication Technologies)
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13 pages, 4438 KiB  
Article
Demonstration of 144-Gbps Photonics-Assisted THz Wireless Transmission at 500 GHz Enabled by Joint DBN Equalizer
by Xiang Liu, Jiao Zhang, Shuang Gao, Weidong Tong, Yunwu Wang, Mingzheng Lei, Bingchang Hua, Yuancheng Cai, Yucong Zou and Min Zhu
Micromachines 2022, 13(10), 1617; https://0-doi-org.brum.beds.ac.uk/10.3390/mi13101617 - 27 Sep 2022
Cited by 2 | Viewed by 1331
Abstract
The THz wireless transmission system based on photonics has been a promising candidate for further 6G communication, which can provide hundreds of Gbps or even Tbps data capacity. In this paper, 144-Gbps dual polarization quadrature-phase-shift-keying (DP-QPSK) signal generation and transmission over a 20-km [...] Read more.
The THz wireless transmission system based on photonics has been a promising candidate for further 6G communication, which can provide hundreds of Gbps or even Tbps data capacity. In this paper, 144-Gbps dual polarization quadrature-phase-shift-keying (DP-QPSK) signal generation and transmission over a 20-km SSMF and 3-m wireless 2 × 2 multiple-input multiple-output (MIMO) link at 500 GHz have been demonstrated. To further compensate for the linear and nonlinear distortions during the fiber–wireless transmission, a novel joint Deep Belief Network (J-DBN) equalizer is proposed. Our proposed J-DBN-based schemes are mainly optimized based upon the constant modulus algorithm (CMA) and direct-detection least mean square (DD-LMS) equalization. The results indicate that the J-DBN equalizer has better bit error rate (BER) performance in receiver sensitivity. In addition, the computational complexity of the J-DBN-based equalizer can be approximately 46% lower than that of conventional equalizers with similar performance. To our knowledge, this is the first time that a novel joint DBN equalizer has been proposed based on classical algorithms. It is a promising scheme to meet the demands of future fiber–wireless integration communication for low power consumption, low cost, and high capacity. Full article
(This article belongs to the Special Issue Broadband Terahertz Devices and Communication Technologies)
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15 pages, 15121 KiB  
Article
Secure Transmission of Terahertz Signals with Multiple Eavesdroppers
by Yuqian He, Lu Zhang, Shanyun Liu, Hongqi Zhang and Xianbin Yu
Micromachines 2022, 13(8), 1300; https://0-doi-org.brum.beds.ac.uk/10.3390/mi13081300 - 12 Aug 2022
Cited by 5 | Viewed by 1174
Abstract
The terahertz (THz) band is expected to become a key technology to meet the ever-increasing traffic demand for future 6G wireless communications, and a lot of efforts have been paid to develop its capacity. However, few studies have been concerned with the transmission [...] Read more.
The terahertz (THz) band is expected to become a key technology to meet the ever-increasing traffic demand for future 6G wireless communications, and a lot of efforts have been paid to develop its capacity. However, few studies have been concerned with the transmission security of such ultra-high-speed THz wireless links. In this paper, we comprehensively investigate the physical layer security (PLS) of a THz communication system in the presence of multiple eavesdroppers and beam scattering. The method of moments (MoM) was adopted so that the eavesdroppers’ channel influenced by the PEC can be characterized. To establish a secure link, the traditional beamforming and artificial noise (AN) beamforming were considered as transmission schemes for comparison. For both schemes, we analyzed their secrecy transmission probability (STP) and ergodic secrecy capacity (ESC) in non-colluding and colluding cases, respectively. Numerical results show that eavesdroppers can indeed degrade the secrecy performance by changing the size or the location of the PEC, while the AN beamforming technique can be an effective candidate to counterbalance this adverse effect. Full article
(This article belongs to the Special Issue Broadband Terahertz Devices and Communication Technologies)
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13 pages, 5658 KiB  
Article
A Dual-Band Eight-Element MIMO Antenna Array for Future Ultrathin Mobile Terminals
by Chuanba Zhang, Zhuoni Chen, Xiaojing Shi, Qichao Yang, Guiting Dong, Xuanhe Wei and Gui Liu
Micromachines 2022, 13(8), 1267; https://0-doi-org.brum.beds.ac.uk/10.3390/mi13081267 - 06 Aug 2022
Cited by 13 | Viewed by 1395
Abstract
An ultrathin dual-band eight-element multiple input–multiple output (MIMO) antenna operating in fifth-generation (5G) 3.4–3.6 GHz and 4.8–5 GHz frequency bands for future ultrathin smartphones is proposed in this paper. The size of a single antenna unit is 9 × 4.2 mm2 (0.105 [...] Read more.
An ultrathin dual-band eight-element multiple input–multiple output (MIMO) antenna operating in fifth-generation (5G) 3.4–3.6 GHz and 4.8–5 GHz frequency bands for future ultrathin smartphones is proposed in this paper. The size of a single antenna unit is 9 × 4.2 mm2 (0.105 λ × 0.05 λ, λ equals the free-space wavelength of 3.5 GHz). Eight antenna units are structured symmetrically along with two sideboards. Two decoupling branches (DB1 and DB2) are employed to weaken the mutual coupling between Ant. 1 and Ant. 2 and between Ant. 2 and Ant. 3, respectively. The measured −10 dB impedance bands are 3.38–3.82 GHz and 4.75–5.13 GHz, which can entirely contain the desired bands. Measured isolation larger than 14.5 dB and 15 dB is obtained in the first and second resonant modes, respectively. Remarkable consistency between the simulated and measured results can be achieved. Several indicators, such as the envelope correlation coefficient (ECC), diversity gain (DG), total active reflection coefficient (TARC), and multiplexing efficiency (ME), have been presented to assess the MIMO performance of the designed antenna. Full article
(This article belongs to the Special Issue Broadband Terahertz Devices and Communication Technologies)
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13 pages, 6541 KiB  
Article
A 66–76 GHz Wide Dynamic Range GaAs Transceiver for Channel Emulator Application
by Peigen Zhou, Chen Wang, Jin Sun, Zhe Chen, Jixin Chen and Wei Hong
Micromachines 2022, 13(5), 809; https://0-doi-org.brum.beds.ac.uk/10.3390/mi13050809 - 23 May 2022
Cited by 1 | Viewed by 1763
Abstract
In this study, we developed a single-channel channel emulator module with an operating frequency covering 66–67 GHz, including a 66–76 GHz wide dynamic range monolithic integrated circuit designed based on 0.1 µm pHEMT GaAs process, a printed circuit board (PCB) power supply bias [...] Read more.
In this study, we developed a single-channel channel emulator module with an operating frequency covering 66–67 GHz, including a 66–76 GHz wide dynamic range monolithic integrated circuit designed based on 0.1 µm pHEMT GaAs process, a printed circuit board (PCB) power supply bias network, and low-loss ridge microstrip line to WR12 (60–90 GHz) waveguide transition structure. Benefiting from the on-chip multistage band-pass filter integrated at the local oscillator (LO) and radio frequency (RF) ends, the module’s spurious components at the RF port were greatly suppressed, making the module’s output power dynamic range over 50 dB. Due to the frequency-selective filter integrated in the LO chain, each clutter suppression in the LO chain exceeds 40 dBc. Up and down conversion loss of the module is better than 14 dB over the 66–67 GHz band, the measured IF input P1 dB is better than 10 dBm, and the module consumes 129 mA from a 5 V low dropout supply. A low-loss ridged waveguide ladder transition was designed (less than 0.4 dB) so that the output interface of the module is a WR12 waveguide interface, which is convenient for direct connection with an instrument with E-band (60–90 GHz) waveguide interface. Full article
(This article belongs to the Special Issue Broadband Terahertz Devices and Communication Technologies)
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13 pages, 19824 KiB  
Article
THz MEMS Switch Design
by Yukang Feng, Han-yu Tsao and N. Scott Barker
Micromachines 2022, 13(5), 745; https://0-doi-org.brum.beds.ac.uk/10.3390/mi13050745 - 08 May 2022
Cited by 6 | Viewed by 2073
Abstract
In this work, an mm-wave/THz MEMS switch design process is presented. The challenges and solutions associated with the switch electrical design, modeling, fabrication, and test are explored and discussed. To investigate the feasibility of this design process, the switches are designed on both [...] Read more.
In this work, an mm-wave/THz MEMS switch design process is presented. The challenges and solutions associated with the switch electrical design, modeling, fabrication, and test are explored and discussed. To investigate the feasibility of this design process, the switches are designed on both silicon and fused quartz substrate and then tested in the 140–750 GHz frequency range. The measurement fits design expectations and simulation well. At 750 GHz the measurement results from switches on both substrates have an ON state insertion loss of less than 3 dB and an OFF state isolation larger than 12 dB. Full article
(This article belongs to the Special Issue Broadband Terahertz Devices and Communication Technologies)
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19 pages, 18142 KiB  
Article
A W-Band Communication and Sensing Convergence System Enabled by Single OFDM Waveform
by Nazar Muhammad Idrees, Zijie Lu, Muhammad Saqlain, Hongqi Zhang, Shiwei Wang, Lu Zhang and Xianbin Yu
Micromachines 2022, 13(2), 312; https://0-doi-org.brum.beds.ac.uk/10.3390/mi13020312 - 17 Feb 2022
Cited by 2 | Viewed by 1499
Abstract
Convergence of communication and sensing is highly desirable for future wireless systems. This paper presents a converged millimeter-wave system using a single orthogonal frequency division multiplexing (OFDM) waveform and proposes a novel method, based on the zero-delay shift for the received echoes, to [...] Read more.
Convergence of communication and sensing is highly desirable for future wireless systems. This paper presents a converged millimeter-wave system using a single orthogonal frequency division multiplexing (OFDM) waveform and proposes a novel method, based on the zero-delay shift for the received echoes, to extend the sensing range beyond the cyclic prefix interval (CPI). Both simulation and proof-of-concept experiments evaluate the performance of the proposed system at 97 GHz. The experiment uses a W-band heterodyne structure to transmit/receive an OFDM waveform featuring 3.9 GHz bandwidth with quadrature amplitude modulation (16-QAM). The proposed approach successfully achieves a range resolution of 0.042 m and a speed resolution of 0.79 m/s with an extended range, which agree well with the simulation. Meanwhile, based on the same OFDM waveform, it also achieves a bit-error-rate (BER) 102, below the forward error-correction threshold. Our proposed system is expected to be a significant step forward for future wireless convergence applications. Full article
(This article belongs to the Special Issue Broadband Terahertz Devices and Communication Technologies)
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Review

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23 pages, 7183 KiB  
Review
Terahertz Reconfigurable Intelligent Surfaces (RISs) for 6G Communication Links
by Fengyuan Yang, Prakash Pitchappa and Nan Wang
Micromachines 2022, 13(2), 285; https://0-doi-org.brum.beds.ac.uk/10.3390/mi13020285 - 10 Feb 2022
Cited by 35 | Viewed by 8177
Abstract
The forthcoming sixth generation (6G) communication network is envisioned to provide ultra-fast data transmission and ubiquitous wireless connectivity. The terahertz (THz) spectrum, with higher frequency and wider bandwidth, offers great potential for 6G wireless technologies. However, the THz links suffers from high loss [...] Read more.
The forthcoming sixth generation (6G) communication network is envisioned to provide ultra-fast data transmission and ubiquitous wireless connectivity. The terahertz (THz) spectrum, with higher frequency and wider bandwidth, offers great potential for 6G wireless technologies. However, the THz links suffers from high loss and line-of-sight connectivity. To overcome these challenges, a cost-effective method to dynamically optimize the transmission path using reconfigurable intelligent surfaces (RISs) is widely proposed. RIS is constructed by embedding active elements into passive metasurfaces, which is an artificially designed periodic structure. However, the active elements (e.g., PIN diodes) used for 5G RIS are impractical for 6G RIS due to the cutoff frequency limitation and higher loss at THz frequencies. As such, various tuning elements have been explored to fill this THz gap between radio waves and infrared light. The focus of this review is on THz RISs with the potential to assist 6G communication functionalities including pixel-level amplitude modulation and dynamic beam manipulation. By reviewing a wide range of tuning mechanisms, including electronic approaches (complementary metal-oxide-semiconductor (CMOS) transistors, Schottky diodes, high electron mobility transistors (HEMTs), and graphene), optical approaches (photoactive semiconductor materials), phase-change materials (vanadium dioxide, chalcogenides, and liquid crystals), as well as microelectromechanical systems (MEMS), this review summarizes recent developments in THz RISs in support of 6G communication links and discusses future research directions in this field. Full article
(This article belongs to the Special Issue Broadband Terahertz Devices and Communication Technologies)
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