THz and Sub-THz CMOS Electronics for High-Speed Telecommunication

Table of Contents

1. Frontmatter

2. Chapter 1. Introduction

   Carl D’heer, Patrick Reynaert

   Abstract

   Fueled by data-intensive applications and global connectivity demands, telecommunication is experiencing a rapid shift. To address the exponential data rate needs of future mobile networks (6G and beyond), the sub-THz (100–300 GHz) and THz (0.3–3 THz) bands hold immense promise. These bands offer vast untapped bandwidths for ultra-high data rates and transformative applications. CMOS technology emerges as an attractive solution for (sub-)THz transceiver ICs due to its established large-scale, low-cost production and potential for digital integration. However, significant challenges exist at these high frequencies. This chapter explores the historical context of telecommunication, delves into the benefits and drawbacks of sub-THz and THz communication, and examines the potential of CMOS for cost-effective, integrated (sub-)THz transceivers, paving the way for widespread adoption in future networks.

3. Chapter 2. Fundamentals of Telecommunication

   Carl D’heer, Patrick Reynaert

   Abstract

   Telecommunication networks are complex systems with many different blocks. In order to tap the full potential of high-speed networks, the properties and design trade-offs of these blocks must be fully understood. This chapter therefore discusses the most fundamental theoretical concepts in telecommunication systems. Starting with a brief review of important mathematical ideas, digital modulation is introduced with an overview of the most prevalent modulation techniques and implementations. Then, the general framework of a communication system is discussed along with the most critical factors that affect performance: noise, nonlinearity, and bandlimiting filtering. Finally, the most promising modulation techniques are compared and their fundamental trade-offs revealed.

4. Chapter 3. Basic Electronics and Components

   Carl D’heer, Patrick Reynaert

   Abstract

   Starting from Maxwell’s fundamental electromagnetic equations, circuit theory can be derived as an approximation in specific situations. Transmission line theory, the foundation of high-frequency RF circuit design, can then be seen as the middle ground between hardcore electromagnetism and simplified circuit theory. Integrated circuits are implemented using both active and passive components. Active devices (mostly transistors) can be used to provide signal amplification, while the passive devices (inductors, transformers, capacitors, and transmission lines) take care of interconnects and ensure optimal operation at high frequencies. In this chapter, the fundamental physics and circuit theory required for high-frequency circuit design are discussed. Then, the primary active and passive components are introduced and their behavior is described.

5. Chapter 4. High-Frequency Circuit Design

   Carl D’heer, Patrick Reynaert

   Abstract

   The previous chapter has illustrated how both the active and passive components have sub-optimal performance at higher frequencies that only degrades as CMOS nodes are scaling down. Meticulous design techniques are hence necessary to realize high-frequency circuits with maximal performance and efficiency. This chapter therefore discusses the basics of impedance matching, resonators, and matching networks which are crucial in RF circuit design. Then, the two primary building blocks for high-frequency amplifiers above 100 GHz in this book are detailed: the neutralized pseudo-differential pair and transformer-based matching network. Finally, the designs of various amplifier-based circuits are discussed.

6. Chapter 5. System-Level Considerations

   Carl D’heer, Patrick Reynaert

   Abstract

   The demand for higher data rates is continuously rising as is the necessity for energy-efficient systems. The high complexity of communication systems characterized by many degrees of freedom makes it rather challenging to identify the optimal ways toward improvement. This chapter attempts to reveal the most essential high-level trade-offs in mm-Wave links, using Shannon’s capacity equation as a starting point. First, a qualitative discussion of the different system-level choices will be given. Then, the limitations in data rate and energy efficiency will be modeled in a quantitative manner, providing an overview of the primary performance bottlenecks in mm-Wave communication systems.

7. Chapter 6. A High-Speed 390 GHz BPOOK Transmitter

   Carl D’heer, Patrick Reynaert

   Abstract

   This chapter details the design of a high-speed 390 GHz BPOOK transmitter in 28 nm CMOS. The objective of this project was to investigate transmitter architectures to exploit the large available bandwidth in the THz frequency range. The modulation, architecture, and circuit design are thus optimized for data rate as well as THz output power.

   First an overview is given of possible THz transmitter architectures with their respective advantages and disadvantages. The central modulation of this system, binary-phase on–off keying or BPOOK, will be extensively studied in the next section. The subsequent sections will then cover the architecture, circuit design, and measurements results of the designed 390 GHz transmitter. Based on the transmitter’s performance, the tripler-based architecture is reassessed and compared to its 130 GHz tripler-less transmitter equivalent. Finally, the chapter is concluded.

8. Chapter 7. A 135 GHz Direct-Digital 16-QAM Wireless and DWG Link

   Carl D’heer, Patrick Reynaert

   Abstract

   This chapter discusses the complete design of a 135 GHz direct-digital 16-QAM wireless and dielectric waveguide (DWG) link in 28 nm CMOS. The aim of this project was to develop a complete sub-THz link over a wireless and dielectric waveguide channel achieving very high data rates while trying to minimize the energy consumption of the system. First the challenges of conventional high-speed transceiver architectures are discussed, and the direct-digital system architecture is introduced. The complete 16-QAM system is described next and system-level specifications are determined. The circuit design of the transmitter and receiver is then elaborately discussed along with chip-level simulations. Design considerations of the high-frequency board are illustrated, including the on-board antenna and coupler. Finally, measurement results of the standalone chips and complete link are discussed, and the performance of the whole system is concluded.

9. Chapter 8. Conclusion

   Carl D’heer, Patrick Reynaert

   Abstract

   This chapter aims to give an overview of the discussed topics in this book with the most important conclusions, starting from the properties of high-frequency waves and CMOS technology, and going all the way to fully implemented high-speed links.

10. Backmatter