Novel D-Band Up-Conversion Mixer Designs in 130-nm SiGe BiCMOS Technology

Licentiatavhandling, 2025

The rapid advancement of digital technologies and the increasing demand for ultra-fast, reliable, and low-latency communication systems have driven the exploration of higher-frequency bands, such as the D-band (110–170 GHz), for next-generation wireless networks. This thesis addresses the critical challenges in designing high-performance up-conversion mixers for D-band communication systems. The D-band, with its wide bandwidth and compact implementation potential, is particularly promising for high-capacity backhaul links, satellite communications, and advanced imaging systems. However, designing mixers for this frequency range presents significant challenges, including achieving high linearity, output power, wide bandwidth, local oscillator suppression, I-Q imbalance (for I-Q mixers), noise, energy efficiency, and circuit compactness while maintaining high isolation between ports.
To address these challenges, in this thesis, two novel mixer architectures are proposed: a cascode mixer and a Darlington mixer, both implemented using 130-nm SiGe BiCMOS technology. The cascode mixer employs a double-mixing technique within a balanced cascode topology, where the first stage (common-emitter transistors) performs initial signal conversion, and the second stage (common-base transistors) enhances the RF signal through double mixing. This design achieves high linearity, robust LO-RF isolation, and enhanced RF output power, making it suitable for high-performance D-band communication systems. On the other hand, the Darlington mixer leverages the Darlington configuration to improve current gain and bandwidth while maintaining low DC power consumption, offering a compelling balance between performance and energy efficiency, making it ideal for low-power and low-voltage applications. Both designs were fabricated and tested, demonstrating competitive figures of merit (FOM) in terms of linearity, isolation, and power efficiency.