The ubiquitous use of electronic devices has led to an explosive increase in the amount of data transfer across the globe. Several applications such as media sharing, cloud computing, Internet of things (IoT), big-data applications demand high performance interconnects to achieve high data rate communication. The mm-wave/terahertz band offers several gigahertz of spectrum for high data rate communication applications. This thesis explores millimeter-wave/terahertz circuits and terahertz systems for various applications in CMOS technology. Some of them include links for personal area networks, wireless backhauls, chip to chip communication (short-range) links in form factor constrained devices (wireless in a box) and also for long-range high-speed communication (using phased arrays or lenses).

In particular, this research explores the feasibility of millimeter-wave/terahertz systems and also the performance of critical blocks such as power amplifiers. A linear power amplifier is designed in a deeply scaled technology node (28 nm) and the various challenges in the design process are discussed. The performance is validated using measurement results and compared across various technology nodes. Non-linear millimeter-wave switching power amplifiers are also explored due to their high efficiencies and a prototype is fabricated to verify the modeling and simulation results.

The ideas and modeling strategies from the individual blocks are used in the design of mm-wave/terahertz transceivers. Simple modulation schemes such as on-off keying, binary phase shift keying and quadrature phase shift keying are used for transmission of data. Two transceiver prototypes with different transmitter and receiver architectures are fabricated in bulk CMOS technology. The system level considerations and architecture choices are discussed. Theoretical analysis of critical blocks with design choices are explained along with their implementation details. The system level measurements from the two transceivers confirm the feasibility of such links at millimeter-wave/terahertz frequencies. The work from this thesis demonstrates the world's first fully functional link at frequencies greater than 200 GHz in CMOS technology.