Terahertz Antenna Research Articles

Modified bow-tie antenna array with efficient electric near-field enhancement for terahertz band

Antenna arrays can induce strong electric near-field enhancement to improve the performance of biological imaging resolution, macromolecule detection sensitivity, and sensing accuracy. However, the use of antenna arrays to regulate both the electric near-field enhancement factor and area has rarely been reported. In this paper, a novel modified bow-tie (MBT) antenna array is proposed for better near-field enhancement performance in terahertz (THz) regime. Using commercially available high frequency structure simulator (HFSS), the dimensions of the MBT antenna array, including gap width, arm length, array period, and substrate thickness, are optimized to improve electric near-field enhancement performance in terms of higher factor, larger area, more controllable peak frequency, and wider 1-dB bandwidth. The as-optimized MBT and bow-tie (BT) THz antenna arrays are fabricated on quartz substrate via lithography and lift-off process. The normalized transmittances of the MBT and BT antenna arrays are characterized by THz time-domain spectroscopy (THz-TDS) and compared with the corresponding simulated near-field enhancement factor and normalized transmittance. The results indicate that the MBT antenna array outperforms the BT antenna array with a three-fold increase in near-field enhancement area and a 66.7% wider 1-dB bandwidth, and therefore can be used to enhance detection sensitivity and sensing accuracy in weak terahertz environment.

A space terahertz antenna fabricated by 3d printing technology

In this paper, a case of space high-precision THz antennas based on 3D printing technology in engineering has been proposed. The reflectors and the supporting structure have been printed in an integrated way by adopting the structural optimization design method suitable for the high-precision 3D printing process and using the honeycomb structure in the low-stress area. This can avoid the assembly error caused by the assembly of various components of the antenna and achieve the goal of integrated, high-precision, lightweight, and high-thermal stability 3D printing, and manufacturing, which provides an idea for high-precision manufacturing of 3D printing technology in space-borne THz devices.

Simultaneous Terahertz Imaging With Information and Power Transfer (STIIPT)

Terahertz (THz) band transmission has the potential to revolutionize future-generation wireless networks by jointly meeting communication and non-communication demands of their connected devices. Recent advances in THz semiconductor technologies and antenna design are closing the THz band gap in millimeter-scale devices which are often battery-limited. The localization of these mobile devices in future wireless networks is of paramount significance for beamforming to overcome THz propagation loss. Consequently, prospective signal processing techniques with co-design architectures are emerging either for joint communication and sensing or for simultaneous information and power transfer. In this paper, we present a novel approach toward Simultaneous Terahertz Imaging with Information and Power Transfer (STIIPT) from a base station transceiver to an Integrated Receiver (IntRx). Leveraging the proposed non-linear rectenna model for energy harvesting, a customized On-Off Keying (cOOK) modulation scheme is proposed for simultaneous communication through a non-linear THz channel while generating a radar-like image to localize the IntRx acting as a target. The proposed theoretical models are corroborated with simulations using a THz band GaAs Schottky diode to demonstrate STIIPT performances which also emphasize the significance of ranging information to optimize rate–energy transfer tradeoff under the cOOK modulation scheme.

A micro-scaled graphene-based wideband (0.57–1.02 THz) patch antenna for terahertz applications

A compact microstrip antenna for terahertz applications is proposed and its characteristic parameters are analyzed by utilizing several conducting and dielectric materials. The proposed terahertz antenna consists of a modified E-shaped patch and slot loaded T-shaped ground plane. The proposed THz antenna structure is designed on a 45 µm thick Rogers RT/Duroid 6010™ substrate with grapheme as a conducting material. The performance parameters are analyzed using High Frequency Structure Simulator and the optimized dimension of the antenna is 130 × 100 µm2. The graphene based designed antenna exhibits a wide impedance bandwidth (IBW) of 450 GHz from 0.57 to 1.02THz with a fractional impedance bandwidth (FBW) of 56.60%. The designed E-shaped antenna shows significant improvements in its FBW and bandwidth dimension ratio (BDR) due to the incorporation of rectangular slot in the T-shaped ground plane. The suggested antenna offers maximum reflection coefficient (S11) of −19.49 dB, adequate VSWR (<2) over operating band, peak gain of 3.47dBi, peak radiation efficiency of 92% and bandwidth dimension ratio (BDR) of 1206.05. Furthermore, effects of different dielectric materials (Rogers RT/Duroid 6010, Polyamide, Sio2, Arlon CE 1000) and conducting materials (copper, silver, graphene and gold) on the performance of the proposed antenna are investigated and discussed. The suggested THz antenna is suitable for ultra – speed short distance communication, medical, imaging and sensing applications in THz region.

Design and performance enhancement of terahertz photoconductive antenna based on nano-crossline contacts

Photoconductive antennas (PCAs) of high conversion efficiency is an essential device for generating or detecting terahertz (THz) waves. This paper presents an enhanced THz-PCA by incorporating buried nano-crosslines (BN-CL) contacts to offer high optical-to-terahertz power conversion efficiency. The BN-CL contact makes that most photocarriers are created at nanoscale distances from the PCA electrodes and, hence, carries drift in a sub-picosecond duration to generate THz radiation. The full-wave multiphysics model is used for the hybrid simulation of THz PCAs and investigated the impact of geometrical variables on a proposed PCA's transient photocurrent. The designed THz antenna has a bandwidth of more than 4 THz and high efficiency of 94%. Both designs of BN-CL and N-CL are implemented with and without double dielectric layers of anti-reflection coating (ARC) and distributed Bragg reflector (DBR) layers. The obtained results of the transient photocurrent are 891 μA and 1089 μA for 10 elements of implemented BN-CL and N-CL contacts, respectively. The photocurrent of BN-CL contacts is enhanced to 1464 μA when 50 element contacts are used. Also, the conversion efficiency of this PCA reaches a maximum value of 1.032% at a pump power of 1.5 mW.

Terahertz Communications for 6G and Beyond Wireless Networks: Challenges, Key Advancements, and Opportunities

The unprecedented increase in wireless data traffic, predicted to occur within the next decade, is motivating academia and industries to look beyond contemporary wireless standards and conceptualize the sixth-generation (6G) wireless networks. Among various promising solutions, terahertz (THz) communications (THzCom) is recognized as a highly promising technology for the 6G and beyond era, due to its unique potential to support terabit-per-second transmission in emerging applications. This article delves into key areas for developing end-to-end THzCom systems, focusing on physical, link, and network layers. Specifically, we discuss the areas of THz spectrum management, THz antennas and beamforming, and the integration of other 6Genabling technologies for THzCom. For each area, we identify the challenges imposed by the unique properties of the THz band.We then present main advancements and outline perspective research directions in each area to stimulate future research efforts for realizing THzCom in 6G and beyond wireless networks.

On-Chip Terahertz antenna array based on amalgamation of metasurface-inspired and artificial magnetic conductor technologies for next generation of wireless electronic devices

The paper presents a feasibility study on an innovative terahertz (THz) on-chip antenna array designed to reliably meet the high-performance connectivity requirements for next generation of wireless devices to enable bandwidth intensive applications, superfast fast streaming, bulk data exchange between internet of things (IoT) devices/smartphones and the development of holographic video conferencing. The significantly smaller wavelength of the THz-band and metasurface-inspired and artificial magnetic conductor (AMC) technologies are exploited here to realize an on-chip antenna. Several experimental on-chip antenna arrays of various matrix sizes were investigated for application at millimeter-wave/Terahertz RF front-end transceivers. The technique proposed here is shown to enhance the antennas impedance bandwidth, gain and radiation efficiency. Purely for experimental purposes a 2 × 24 radiation element array was fabricated. It exhibits an average measured gain of 20.36 dBi and radiation efficiency of 37.5% across 0.3–0.314 THz. For proof of the concept purposes a THz receiver incorporating the proposed on-chip antenna was modelled. The results show that with the proposed antenna array a THz receiver can provide a gain of 25 dB when the antenna is directly matched to low-noise amplifier stage.

Secrecy Capacity of IRS-Assisted Terahertz Wireless Communications With Pointing Errors

This letter considers an intelligent reflecting surface (IRS)-assisted terahertz (THz) communication system in the presence of an arbitrary number of colluding/non-colluding eavesdroppers (Eves). Although the instantaneous channel state information (CSI) of the legitimate user (Bob) is assumed to be available, the IRS with discrete phase shifters cannot achieve optimal phase shifts, and thus Bob suffers from phase shift quantization errors. By taking into account the availability of the statistical CSI of Eves, pointing errors caused by highly-directional THz antennas, and the phase shift quantization errors, new expressions for the secrecy capacity in both cases of Eves are derived. The accuracy of the expressions is then verified by Monte-Carlo simulations. These expressions are used to investigate the impacts of pointing errors and quantization errors on the physical layer security of IRS-assisted THz systems in the presence of colluding and non-colluding Eves.

Particle Swarm Optimization Based Design of a Terahertz Antenna with a Modified Photonic Band Gap Substrate for 6G Future Wireless Communications

In this study, an antenna is proposed that operates at THz spectrum for sixth generation (6G) short-range future wireless communications. A modified photonic band gap (MPBG) substrate is employed to design an octagonal ring shaped microstrip patch antenna with wideband and high gain properties. Unlike the conventional photonic band gap (PBG) form, the proposed MPBG substrate structure is created by variable sized cylindrical air holes. The radii of each air cylinder in the row is determined with the help of particle swarm optimization (PSO) algorithm, where the goal is set to achieve the highest gain and impedance bandwidth (S_11≤-10 dB) possible. The simulation results of the antennas that are built on 1) non-PBG, 2) conventional PBG and 3) the proposed MPBG substrate structures are compared. It is observed that the radiation performance is most enhanced by implementing MPBG structure. In comparison to the antenna without PBG, the reported MPBG structure offers almost 300% gain and 11% bandwidth improvement. To summarize, the designed antenna with its proposed MPBG substrate structure achieves an excellent radiation performance within a wide operating bandwidth.

Comparison of Diverse Shaped Graphene Microstrip Patch Terahertz Antennas and Performance Investigation of Penta Model on Disparate Substrates

Comparison of Diverse Shaped Graphene Microstrip Patch Terahertz Antennas and Performance Investigation of Penta Model on Disparate Substrates

Experimental and Computational Analysis of Broadband THz Photoconductive Antennas

The work presents the fabrication and measurements of four LT-GaAs photoconductive terahertz (THz) antennas with different geometries of metallic electrodes. The goal is to analyze the overall bandwidth of the antennas through a comparison between the spectra of the generated photocurrent in the antenna gap, the radiated electric field THz pulse, and the S11 parameter of the metallic electrodes. The photocurrent density and the S11 parameters are computed using COMSOL multiphysics, while the generated THz pulse was experimentally measured using a time-domain spectroscopy system. The polarizations of the photoconductive antennas are experimentally measured, using x-cut quartz crystal halfwave plates, showing polarization in the direction of the electrode’s long axis. Pinholes are used to verify system alignment and quality of the radiated signal spectra. The results show that the spectra of the radiated THz pulses in all four antennas considered in this work are dominated by the behavior of the S11 parameter at the lower part of the frequency band, but with the decreasing photocurrent dominating the spectra at higher frequencies.

Implementing the circularly polarized THz antenna with tunable filtering characteristics

An ultra-wideband (UWB) terahertz (THz) antenna is designed and numerically analyzed. A technique is implemented for obtaining the filtering characteristics in the antenna response. A graphene sheet is placed in antenna structure for achieving the filtering response. The variation in the surface conductivity of the covered area by graphene sheet provides the variable field confinement in antenna structure. This way helps in generating the filtering characteristics in UWB response of antenna. Also, the variation in the electrical properties of graphene material provides the tunability in the generated notched frequency band. The antenna utilizes the feeding with the orthogonal stubs associated with it which helps in providing the circularly polarized response. Furthermore, the antenna operation is verified with the electrical circuit model.

Review of Terahertz Antenna Technology for Science Missions in Space

The utilization of terahertz (THz) band in the electromagnetic spectrum has great potential value both in scientific research and practical applications, therefore reasonable design of antenna system for radiating and receiving THz wave is especially critical. This article reviews the THz antenna technology toward atmospheric remote sensing, radio astronomy, and deep space exploration over the past three decades. Some typical scientific and engineering applications in space are discussed, which include the specifications, design issues, and the performance of various space THz antenna systems. Horn array antennas (synthetic aperture radiometry), reflector antennas fed by quasi-optical networks and traditional microwave networks have been widely applied in the designs for science missions. Finally, some promising THz antennas for future missions are introduced, and viewpoints on research challenges and future directions are given.

A triband EBG loaded microstrip fractal antenna for THz application

Future wireless communication needs antenna with multifunctional operation. This paper focuses on Terahertz Antenna that could be easily integrated with micro and nano devices. In this paper, an octagonal shaped Microstrip Fractal Antenna loaded with the EBG structure is designed for tri-band terahertz application. Triple band characteristic achieved by fractal radiating patch is loaded with Electronic Band Gap (EBG). The antenna is working on triple band characteristics at 948 GHz, 984GHz and, 1040 GHz with overall dimensions of 700x900 µm2. The result and performance show that the recommended antenna will be compatible with compact wireless devices and Monolithic Microwave Integrated Circuit (MMIC). All simulation work has been done using electromagnetic software Ansoft High Frequency Structure Simulator (HFSS) and CST studio suite. The electromagnetic features like S11 parameters, VSWR, gain, efficiency and the radiation characteristics of such antenna are also explored. The simulation results show that this antenna has 9 dB realized gain at 0.948 THz resonating frequency.

Terahertz antenna with tunable filtering.

A terahertz (THz) antenna with tunable filtering is designed and numerically studied. A slotted monopole radiator with defected ground structure is used for operating with wideband response with an impedance bandwidth in the range of 3.80-11.98THz for S 11≤-10d B. A slot is engraved in the radiator for obtaining the filtering characteristics in the antenna response. By varying its chemical potential, the frequency band 5.05-6.69THz with graphene material can provide the tunability in the frequency and bandwidth of the filtered band in the antenna response. Furthermore, the antenna can provide radiation efficiency of more than 90% and gain with a peak value of 6.6dBi in the passband.

THz Measurements, Antennas, and Simulations: From the Past to the Future

In recent years, terahertz (THz) systems have become an increasingly popular area of research thanks to their unique properties such as extremely high data rates towards Tb/s, submillimeter localization accuracy, high resolution remote sensing of materials, and remarkable advances in photonics and electronics technologies. This article traces the progress of THz measurements, antennas and simulations, from historical milestones to the current state of research and provides an outlook on the remaining challenges.

Broadband Antenna Design for Terahertz Communication Systems

This paper provides an overview of broadband terahertz antenna elements and arrays for integrated communication systems. The fundamental challenges of integrated on-chip and off-chip antenna design, the trade-offs between performance metrics, and the impact of interface between the chip and off-chip antennas are studied in detail. The limitations and benefits of various interface technologies are discussed. The deployment of printed circuit boards (PCB) and flexible printed circuits (FPC) technologies for implementation of efficient broadband antennas is compared against on-chip counterparts. As a proof of concept, an off-chip antenna for the 91–134 GHz is presented.

An ultra-wideband orthogonal-beam directional graphene-based antenna for THz wireless systems

In terahertz (THz) wireless systems, graphene shows a tremendous promise for the implementation of miniaturized and reconfigurable antennas due to its unique tunable property. This paper presents a wideband beam reconfigurable directional antenna for THz wireless communication systems. The antenna design concept is based on the Yagi-Uda antenna working principle. The proposed antenna consists of a centre-fed graphene-based driven dipole and three graphene-based parasitic elements on either side of the driven element. These graphene-based parasitic elements either act as directors or reflectors by controlling the surface conductivity of these elements. The surface conductivity of the elements is adjusted individually by applying a bias voltage via the chemical potential of the graphene. The main beam direction of the antenna can be reconfigured by controlling the chemical potentials of the graphene-based parasitic elements. Specifically, the proposed graphene THz antenna reconfigures the main beam into four orthogonal directions (0°, 90°, 180° and 270°) at an operational frequency 1.25 THz. The antenna achieves a directional symmetrical radiation pattern with 14 dBi gain and a front-to-back ratio of 15.5 dB. Furthermore, the proposed graphene THz antenna provides a stable reflection coefficient in four reconfigurable cases and an ultra-wideband of 10-dB impedance bandwidth of 120%. Therefore, this novel design technique of graphene-based ultra-wideband high gain beam reconfigurable THz antenna is promising for THz wireless systems.

A Numerical Investigation of Graphene-Based Hilbert-Shaped Multi-Band MIMO Antenna for the Terahertz Spectrum Applications.

We proposed the numerical investigation of Hilbert-shaped multiple-input multi-output (MIMO) with multi-band operation characteristics using graphene resonator material, which operates on the band of 1 to 30 THz of the frequency range. This numerical investigation of antenna structure was carried out for the multiple antenna types, consisting of graphene as a regular patch, Hilbert order 1, and Hilbert order 2 designs. This antenna is investigated for the multiple physical parameters, such as return loss, gain, bandwidth, radiation response, Envelope Correlation Coefficient (ECC), Total Active Reflection Coefficient (TARC), Mean Effective Gain (MEG), Directivity Gain (DG), and Channel Capacity Loss (CCL). These variables are also determined to verify compatibility and the difficulties connected with communicating over a short distance. The THz MIMO antenna that was recommended offers strong isolation values in addition to an operational band. The maximum gain of ~10 dBi for the band of <15 THz and ~17 dBi for the band of the >15 THz frequency range of the proposed antenna structures. The proposed antennas are primarily operated in three bands over 1 to 30 THz of frequency. This work aims to create a brand new terahertz antenna structure capable of providing an extraordinarily wider bandwidth and high gain while keeping a typical compact antenna size suited for terahertz applications.

Terahertz antenna with controllable and tunable filtering characteristics

− A terahertz (THz) wideband antenna is implemented and numerically studied for achieving the controllable and tunable filtering characteristics. A rectangular-shaped metal-based monopole antenna is designed for obtaining the wideband response. A slot is engraved in the radiator to obtain the filtering characteristics. The slot in radiator is filled with graphene material which acts as the controller and tuner of obtained filtering characteristics. The surface conductivity of graphene strip is tuned and hence the field confinement in the covered area is varied which tunes and controls the obtained filtering characteristics. The antenna provides monopole like radiation pattern with a high value of gain and radiation efficiency which decay in the filtered frequency band with a sharp roll-off rate to attain their minimum value. The gain and efficiency of antenna remain approximately unchanged in the passband even after application of graphene in antenna structure. This signifies the effectiveness of the proposed technique for obtaining the filtering characteristics in antenna response. Moreover, the antenna response is validated through an electrical circuit theory approach.