Challenges and Opportunities in D-Band Transmitter Architectures and Antenna Design, Integration, and Scalability for 6G Communications: A Brief Review

This article reviews the current state-of-the-art (SOTA) key enabling technologies that pave the way for the advancement of scalable 6G antenna array systems for future communications. The focus is on the development of transmitter building blocks, considering the implementation of size, weight, area, and power (SWaP) constrained nodes. First, an overview of communication technologies from 1G to 6G is presented, followed by a discussion of key performance indicators and link budget analysis. To provide further insights into D-band (110-170 GHz) system design challenges, this review highlights the significance of 1) high-gain and high-linearity power amplifiers, 2) spectrally pure local oscillator (LO) signal sources, 3) high data rate modulator architectures, 4) scalable antenna array development, and 5) heterogeneous integration approaches. Furthermore, this article presents ongoing research and development on transmitter building blocks across various device fabrication technologies such as CMOS, BiCMOS, and III-V semiconductors. Special attention is given to the high data rate modulator architectures, which comprise 1) heterodyne, 2) homodyne, and 3) direct-digital modulators, followed by addressing the implementation challenges and opportunities in coherent and noncoherent modulation schemes within the context of SWaP-constrained scalable arrays for D-band. Additionally, this article reviews heterogeneous integration (HI) while focusing on chiplet designs for multifunctionality, low-loss packaging trends with thermal management solutions, chip-antenna interconnects featuring novel antenna technologies, and bottlenecks in mmWave/sub-THz measurements.