6G and beyond will fulfill the requirements of a fully connected world and provide ubiquitous wireless connectivity for all. Transformative solutions are expected to drive the surge for accommodating a rapidly growing number of intelligent devices and services. Major technological breakthroughs to achieve connectivity goals within 6G include: (i) a network operating at the THz band with much wider spectrum resources, (ii) intelligent communication environments that enable a wireless propagation environment with active signal transmission and reception, (iii) pervasive artificial intelligence, (iv) large-scale network automation, (v) an all-spectrum reconfigurable front-end for dynamic spectrum access, (vi) ambient backscatter communications for energy savings, (vii) the Internet of Space Things enabled by CubeSats and UAVs, and (viii) cell-free massive MIMO communication networks. In this roadmap paper, use cases for these enabling techniques as well as recent advancements on related topics are highlighted, and open problems with possible solutions are discussed, followed by a development timeline outlining the worldwide efforts in the realization of 6G. Going beyond 6G, promising early-stage technologies such as the Internet of NanoThings, the Internet of BioNanoThings, and quantum communications, which are expected to have a far-reaching impact on wireless communications, have also been discussed at length in this paper.

/pdf/6g-and-beyond-the-future-of-wireless-communications-systems-3jqy8nx3qf.pdf

6G and Beyond: The Future of Wireless Communications Systems

The field of terahertz integrated technology has undergone significant development in the past ten years. This has included work on different substrate technologies such as III–V semiconductors and silicon, work on field-effect transistor devices and heterojunction bipolar devices, and work on both fully electronic and hybrid electronic–photonic systems. While approaches in electronic and photonics can often seem distinct, techniques have blended in the terahertz frequency range and many emerging systems can be classified as photonics-inspired or hybrid. Here, we review the development of terahertz integrated electronic and hybrid electronic–photonic systems, examining, in particular, advances that deliver important functionalities for applications in communication, sensing and imaging. Many of the advances in integrated systems have emerged, not from improvements in single devices, but rather from new architectures that are multifunctional and reconfigurable and break the trade-offs of classical approaches to electronic system design. We thus focus on these approaches to capture the diversity of techniques and methodologies in the field. This Review Article examines the development of terahertz integrated electronic and hybrid electronic–photonic systems, considering, in particular, advances that deliver important functionalities for applications in communication, sensing and imaging.

Terahertz integrated electronic and hybrid electronic–photonic systems

The field of terahertz science and technology has been an active and thriving research area for several decades. However, the field has recently experienced an inflection point, as several exciting breakthroughs have enabled new opportunities for both fundamental and applied research. These events are reshaping the field, and will impact research directions for years to come. In this Perspective article, I discuss a few important examples: the development of methods to access nonlinear optical effects in the terahertz range; methods to probe nanoscale phenomena; and, the growing likelihood that terahertz technologies will be a critical player in future wireless networks. Here, a few examples of research in each of these areas are discussed, followed by some speculation about where these exciting breakthroughs may lead in the near future.

/pdf/perspective-terahertz-science-and-technology-1lfl35we40.pdf

Perspective: Terahertz science and technology

Add this article to private library Remove from private library Submit corrections to this record View record in the new ADS The book presents an introductory treatment of digital and analog communication systems with emphasis on digital systems. Attention is given to the following topics: systems and signal analysis, random signal theory, information and channel capacity, baseband data transmission, analog signal transmission, noise in analog communication systems, digital carrier modulation schemes, error control coding, and the digital transmission of analog signals. Bibtex entry for this abstract Preferred format for this abstract

Digital and analog communication systems

Traditional terahertz (THz) equipment faces major obstacles in providing the system cost and compactness necessary for widespread deployment of THz applications. Because of this, the field of THz integrated circuit (THz IC) design in CMOS and SiGe HBT technologies has surged in the last decade. An interplay of advances in silicon process technology, design technique, and microelectronic packaging promises to narrow the gap between the requirements and the reality of system cost and performance of THz components. Furthermore, the scalability, reconfigurability, and signal processing features of silicon technology have initiated research in complex THz ICs that expand the functionality of THz systems; this has enabled new applications, methods, and algorithms. This paper reviews the progress in THz IC research and investigates several realizations of THz imaging and sensing applications with silicon-based components regarding their motivation, system performance, and challenges. THz computed tomography, broadband multicolor imaging, high-resolution FMCW radar imaging, subwavelength resolution near-field imaging, and compressed sensing are presented.

Terahertz Imaging and Sensing Applications With Silicon-Based Technologies

This paper presents a fully integrated direct-conversion quadrature transmitter and receiver chipset at 240 GHz. It is implemented in a 0.13- $\mu{\hbox{m}}$ SiGe bipolar-CMOS technology. A wideband frequency multiplier ( $\times$ 16) based local-oscillator (LO) signal source and a wideband on-chip antenna designed to be used with an external replaceable silicon lens makes this chipset suited for applications requiring fixed and tunable LO. The chipset is packaged in a low-cost FR4 printed circuit board resulting in a complete solution with compact form-factor. At 236 GHz, the effective-isotropic-radiated-power is 21.86 dBm and the minimum single-sideband noise figure is 15 dB. The usable RF bandwidth for this chipset is 65 GHz and the 6-dB bandwidth is 17 GHz. At the system level, we demonstrate a high data-rate communication system where an external modem is operated in its two IF-bandwidth modes (250 MHz and 1 GHz). For the quadrature phase-shift keying modulation scheme, the measured data rate is 2.73 Gb/s (modem 1-GHz IF) with bit-error rate of ${\hbox{10}}^{-9}$ for a 15-cm link. The estimated data rate over the 17-GHz RF bandwidth is, hence, 23.025 Gb/s. Also, higher order modulation schemes like 16 quadrature amplitude modulation (QAM) with a data rate of 0.677 Gb/s and 64-QAM with a data rate of 1.0154 Gb/s (modem 250-MHz IF) is demonstrated. A second application demonstrator is presented where the wide tunable RF bandwidth of the chipset is used for material characterization. It is used to characterize an FR4 material (DE104) over the 215–260-GHz range.

A Fully Integrated 240-GHz Direct-Conversion Quadrature Transmitter and Receiver Chipset in SiGe Technology

This paper presents a fully integrated direct-conversion quadrature transmitter and receiver chipset at 240 GHz in a 0.13 μm SiGe HBT technology with f T /f max of 350/550 GHz. This chipset is suited for applications requiring both fixed and tunable LO which is made possible due to a wideband frequency multiplier (×16) based local-oscillator (LO) signal source and a wideband on-chip antenna designed to be used with an external replaceable silicon lens. The Tx can deliver up to 6 dBm output power at 240 GHz and the 3-dB bandwidth is 40 GHz. For the Rx, the peak conversion gain is 10 dB and the NF is 15 dB while the 3-dB bandwidth is 28 GHz. The chipset is integrated in a low loss Rogers 4350B COB (chip-onboard) packaging. For communication applications where high IF bandwidth is required, stepped impedance low-pass filters with minimum group delay variations were implemented on the PCB to negate the low-pass characteristics introduced by the bondwire. The measured 6-dB IF bandwidth is 13 GHz. By using this chipset for high data rate communication, the measured EVM for BPSK modulation is 24% at 20 Gbps while the EVM is 30% at 25 Gbps. For the QPSK modulation scheme, an EVM of 24% is measured at 24 Gbps. These results are for a link of 70 cm and without calibrating the effect of the IF cables and without any channel equalization.

A wideband fully integrated SiGe chipset for high data rate communication at 240 GHz

This paper presents a fully-integrated direct-conversion fundamentally-operated mixer-first quadrature receiver chip working at 240 GHz. It has been implemented in a 0.13-μm SiGe HBT technology with f T /f max of 350/550 GHz. The chip includes an LO path based on a x16 multiplier with a 3-stage PA, driven externally from the PCB at 14–18 GHz. The LO signal is split in quadrature by a broadband coupler. It drives two double-balanced fundamentally-operated mixers with their RF ports connected directly to a wideband lens-integrated linearly-polarized on-chip ring antenna. For low-cost packaging, the chip-on-lens assembly is wire-bonded onto a high-speed PCB, where an on-board 8-section step-impedance microstrip-line low-pass filter has been implemented to compensate the wire-bond inductance at the IF outputs. The 3-dB RF/LO operation BW (with fixed IF) is 47 GHz with peak CG of 7.8 dB, and minimum SSB NF of 11.3 dB, whereas a 3-dB IF bandwidth is at least 12 GHz. All measurement results have been taken at the board-level and include the implementation losses of both the antenna and the on-board high-speed interconnects. The receiver IQ amplitude imbalance is below 1.58 dB for the 210–280 GHz band. In combination with a 9-mm silicon lens, the receiver module provides a directivity of 25.2 to 27.04 dBi from 210 to 280 GHz.

A 219–266 GHz fully-integrated direct-conversion IQ receiver module in a SiGe HBT technology

A fully-electronic high-speed transmission with a highly-integrated set of quadrature direct-conversion TX and RX modules in 130nm SiGe HBT technology operating in the 240 GHz transmission window is presented. In view of high packaging costs of the currently available THz communication front-ends, each of the modules is implemented as a single chip with a broadband silicon lens-integrated on-chip antenna and assembled on a low-cost high-speed PCB providing an IF operation bandwidth of 13 GHz at the board-connector level. For the preliminary wireless-link tests at a distance of 1m, a 30 Gbps and a 50 Gbps transmission speed with EVM of 26% and 29% is demonstrated for BPSK and QPSK modulation, respectively, with no channel equalization applied.

A 240 GHz high-speed transmission link with highly-integrated transmitter and receiver modules in SiGe HBT technology

This paper reports on the development and experimental characterization of a high data-rate communication link at 240GHz with highly-integrated direct-conversion quadrature transmitter and receiver modules implemented in 130nm SiGe HBT technology with ft/fmax of 350/550 GHz Both modules employ a low-cost chip-on-board packaging scheme with single-chip TX and RX front-end circuits accommodating wideband silicon lens-integrated wire ring on-chip antennas The key highlights of the developed hardware are its high RF and IF operation bandwidths available from the printed-circuit board-level With the preliminary wireless transmission tests, a 20Gbps and a 24Gbsp transmission speed with an EVM of 24% was demonstrated for BPSK and QPSK modulation schemes at a distance of 90cm with no channel equalization applied For a 10Gbps BPSK, an error-free communication link could be established

Pedro Rodriguez Vazquez

Papers

A Fully Integrated 240-GHz Direct-Conversion Quadrature Transmitter and Receiver Chipset in SiGe Technology

A wideband fully integrated SiGe chipset for high data rate communication at 240 GHz

A 219–266 GHz fully-integrated direct-conversion IQ receiver module in a SiGe HBT technology

A 240 GHz high-speed transmission link with highly-integrated transmitter and receiver modules in SiGe HBT technology

High data-rate communication link at 240 GHz with on-chip antenna-integrated transmitter and receiver modules in SiGe HBT technology