Terahertz Integrated Research Articles

THz ISAC: A Physical-Layer Perspective of Terahertz Integrated Sensing and Communication

THz ISAC: A Physical-Layer Perspective of Terahertz Integrated Sensing and Communication

Empowering 6G Ambient Intelligence with Terahertz Integrated Sensing and Communications

Empowering 6G Ambient Intelligence with Terahertz Integrated Sensing and Communications

Analysis and Design of Tri-Coupled-Line-Based Attenuator for Miniaturized Terahertz Integrated Systems

Analysis and Design of Tri-Coupled-Line-Based Attenuator for Miniaturized Terahertz Integrated Systems

Channel Training-Aided Target Sensing for Terahertz Integrated Sensing and Massive MIMO Communications

Channel Training-Aided Target Sensing for Terahertz Integrated Sensing and Massive MIMO Communications

DFT-Spread Orthogonal Time Frequency Space System With Superimposed Pilots for Terahertz Integrated Sensing and Communication

Terahertz (THz) integrated sensing and communication (ISAC) is a promising interdisciplinary technology that realizes simultaneously transmitting Terabit-per-second (Tbps) and millimeter-level accurate environment or human activity sensing. However, both communication performance and sensing accuracy are influenced by the Doppler effects, which are especially severe in the THz band. Moreover, peak-to-average power ratio (PAPR) degrades the THz power amplifier (PA) efficiency. In this paper, a discrete Fourier transform spread orthogonal time frequency space (DFT-s-OTFS) system with superimposed pilots is proposed to improve the robustness to Doppler effects and reduce PAPR for THz ISAC. Then, a two-phase sensing parameter estimation algorithm is developed to integrate sensing functionality into the DFT-s-OTFS waveform. Meanwhile, a low-complexity iterative channel estimation and data detection method with a conjugate gradient based equalizer is proposed to recover the data symbols of DFT-s-OTFS. The proposed DFT-s-OTFS waveform can improve the PA efficiency by 10% on average compared to OTFS. Simulation results demonstrate that the proposed two-phase sensing estimation algorithm for THz DFT-s-OTFS systems is able to realize millimeter-level range estimation accuracy and decimeter-per-second-level velocity estimation accuracy. Moreover, the effectiveness of the iterative method for data detection aided by superimposed pilots in DFT-s-OTFS systems is validated by the simulations and the bit error rate performance is not degraded by the Doppler effects.

A Compact Hybrid G-band Heterodyne Receiver Integrated with Millimeter Microwave Integrated Circuits and Schottky Diode-Based Circuits

This paper presents a compact hybrid G-band (170–260 GHz) heterodyne receiver module incorporating both Millimeter Microwave Integrated Circuits (MMICs) and a Schottky diode-based circuit. An on-chip sextupler and a Low Noise Amplifier (LNA), along with a diode-based Sub-Harmonic Mixer (SHM), are integrated into the demonstrated singular module, which is carefully designed and arranged with the co-simulations in electromagnetic and thermal domain. Through this methodology, a terahertz receiver module is fabricated with a volume of only 27 × 20 × 20 mm3. The measured results indicate that the double-sideband conversion gain of the receiver is 10.5–17.5 dB from 195 GHz to 230 GHz, while the noise temperature is 1009–1158 K. As a result, this terahertz receiver provides recorded miniaturized hardware applicable for terahertz Integration of Sensing and Communication (ISAC) systems.

Sensing Integrated DFT-Spread OFDM Waveform and Deep Learning-Powered Receiver Design for Terahertz Integrated Sensing and Communication Systems

Terahertz (THz) communications are envisioned as a key technology of next-generation wireless systems due to its ultra-broad bandwidth. One step forward, THz integrated sensing and communication (ISAC) system can realize both unprecedented data rates and millimeter-level accurate sensing. However, THz ISAC meets stringent challenges on waveform and receiver design to fully exploit the peculiarities of THz channel and transceivers. In this work, a sensing integrated discrete Fourier transform spread orthogonal frequency division multiplexing (SI-DFT-s-OFDM) system is proposed for THz ISAC, which can provide lower peak-to-average power ratio than OFDM and is adaptive to flexible delay spread of the THz channel. Without compromising communication capabilities, the proposed SI-DFT-s-OFDM realizes millimeter-level range estimation and decimeter-per-second-level velocity estimation accuracy. In addition, the bit error rate (BER) performance is improved by 5 dB gain at the 10°3 BER level compared with OFDM. At the receiver, a deep learning based ISAC receiver with two neural networks is developed to recover transmitted data and estimate target range and velocity, while mitigating the imperfections and non-linearities of THz systems. Extensive simulation results demonstrate that the proposed deep learning methods can realize mutually enhanced performance for communication and sensing, and is robust against Doppler effects, phase noise and multi-target estimation.

Bi2Se3 Growth on (001) GaAs Substrates for Terahertz Integrated Systems.

Terahertz (THz) technologies have been of interest for many years due to the variety of applications including gas sensing, nonionizing imaging of biological systems, security and defense, and so forth. To date, scientists have used different classes of materials to perform different THz functions. However, to assemble an on-chip THz integrated system, we must understand how to integrate these different materials. Here, we explore the growth of Bi2Se3, a topological insulator material that could serve as a plasmonic waveguide in THz integrated devices, on technologically important GaAs(001) substrates. We explore surface treatments and find that an atomically smooth GaAs surface is critical to achieving high-quality Bi2Se3 films despite the relatively weak film/substrate interaction. Calculations indicate that the Bi2Se3/GaAs interface is likely selenium-terminated and shows no evidence of chemical bonding between the Bi2Se3 and the substrate. These results are a guide for integrating van der Waals materials with conventional semiconductor substrates and serve as the first steps toward achieving an on-chip THz integrated system.

Emerging Terahertz Integrated Systems in Silicon

Silicon-based terahertz (THz) integrated circuits (ICs) have made rapid progress over the past decade. The demonstrated basic component performance, as well as the maturity of design tools and methodologies, have made it possible to build high-complexity THz integrated systems. Such implementations are undoubtedly highly attractive due to their low cost and high integration capability; however, their unique characteristics, both advantageous and disadvantageous, also call for research investigations into unconventional systematic architectures and novel THz applications. In this paper, we review the current status and future trend of silicon-based THz ICs, with the focus on state-of-the-art THz microsystems for emerging sensing and communication applications in the last few years, such as high-resolution imaging, high medium/long-term stability time keeping, high-speed wireline/wireless communications, and miniaturization of RF tags, as well as THz packaging technologies.

On-Chip Antenna Design Using the Concepts of Metamaterial and SIW Principles Applicable to Terahertz Integrated Circuits Operating over 0.6–0.622 THz

This research work presents the investigation of realizing an on-chip antenna based on the metamaterial concept, which is working over the terahertz (THz) band for applications in integrated circuits. The proposed on-chip antenna is constructed of five stacked layers of polyimide and aluminum as top and bottom substrates, radiation patches, ground plane, and feed line. The four square-shaped radiation patches are implemented on the 50 μ m top-polyimide substrate, and the feed line is realized on the 50 μ m bottom-polyimide layer by designing the simple square microstrip lines, which are all connected to each other and then excited by waveguide port. The ground plane including a coupling square slot has sandwiched between the top- and bottom-polyimide layers. The coupling square slot etched on the ground plane is exactly placed under the patch to optimum transfer the electromagnetic signal from the bottom feed line to the top radiation patch. To achieve high performance parameters without increasing the antenna's physical dimensions, the metamaterial and substrate integrated waveguide properties have been applied to the antenna structure by implementing linear tapered slots on the patch top surfaces and metallic via holes throughout the middle ground plane connecting top and bottom substrates to each other. The slots play the role of series left-handed (LH) capacitors (CL) and the via holes act as shunt LH inductors (LL). The overall dimension of the proposed metamaterial-based on-chip antenna is 1000 × 1000 × 100 μm3. This antenna can cover the frequency band from 0.6 THz to 0.622 THz, which is equal to 20 GHz bandwidth. The radiation gain and efficiency across the operating frequency band varies from 1.1 dBi to 1.8 dBi, and from 58% to 60.5%, respectively. The results confirm that the proposed on-chip antenna with compact dimensions, wide bandwidth over the terahertz domain, low profile, cost effective, simple configuration, and easy to manufacture can be potentially appropriate for terahertz integrated circuits.

Broadband Single‐Mode Hybrid Photonic Crystal Waveguides for Terahertz Integration on a Chip

AbstractBroadband, low‐loss, low‐dispersion propagation of terahertz pulses in compact waveguide chips is indispensable for terahertz integration. Conventional 2D photonic crystals (PCs) based terahertz waveguides are either all‐metallic or all‐dielectric, having either high propagation losses due to the Ohmic loss of metal, or a narrow transmission bandwidth restricted by the range of single‐mode operation in a frequency range defined by the PC bandgap, respectively. To address this problem, a hybrid (metal/dielectric) terahertz waveguide chip is developed, where the guided mode is completely confined by parallel gold plates and silicon PCs in vertical and lateral directions, respectively. A unique multiwafer silicon‐based fabrication process, including gold–silicon eutectic bonding, micropatterning, and Bosch silicon etching, is employed to achieve the self‐supporting hybrid structure. Theoretical and experimental investigations demonstrate that the hybrid waveguide supports a single‐mode transmission covering 0.367–0.411 THz (bandwidth of 44 GHz, over twice wider than that of all‐silicon PC waveguides) with low loss (below 0.05 dB mm−1) and low group velocity dispersion (from −8.4 to −0.8 ps THz−1 mm−1). This work enables more compact, wideband terahertz waveguides and auxiliary functional components that are integratable in chips toward ultra‐high‐density integrated terahertz devices in particular in the field of wireless communications.

Optical device terahertz integration in a two-dimensional-three-dimensional heterostructure.

The transmission properties of an off-planar integrated circuit including two wavelength division demultiplexers are designed, simulated, and analyzed in detail by the finite-difference time-domain method. The results show that the wavelength selection for different ports (0.404[c/a] at B2 port, 0.389[c/a] at B3 port, and 0.394[c/a] at B4 port) can be realized by adjusting the parameters. It is especially important that the off-planar integration between two complex devices is also realized. These simulated results give valuable promotions in the all-optical integrated circuit, especially in compact integration.

Extremely low-loss terahertz waveguide based on silicon photonic-crystal slab.

We pursued the extremely low loss of photonic-crystal waveguides composed of a silicon slab with high resistivity (20 kΩ-cm) in the terahertz region. Propagation and bending losses as small as <0.1 dB/cm (0.326-0.331 THz) and 0.2 dB/bend (0.323-0.331 THz), respectively, were achieved in the 0.3-THz band. We also developed 1.5-Gbit/s terahertz links and demonstrated an error-free uncompressed high-definition video transmission by using a photonic-crystal waveguide with a length of as long as 50 cm and up to 28 bends thanks to the low-loss properties. Our results show the potential of photonic crystals for application as terahertz integration platforms.