Upconversion mixer for 300 GHz applications

Abstract

The increasing interest in the sub-THz frequency range due to the potential for higher data rates and wider bandwidths, has been faced with various challenges regarding the signals generation and translation to such high frequencies. The upconversion mixers sits at the core of this problem. They are essential components in transmitters, converting lower-frequency IF signals to higher-frequency RF signals through multiplication with an LO signal. This process prepares the signal for amplification and transmission.

This thesis investigates the theory of upconversion mixers and details their design process from schematic-level circuit design to physical layout design. The design utilizes IHP's 130 nm SiGe BiCMOS technology and is based on the Gilbert cell topology, chosen for its potential advantages in high-frequency applications. The mixer aims to upconvert an IF signal centered around 100 GHz to an RF signal centered around 300 GHz.

The final mixer layout, incorporating integrated transformers for impedance matching, achieved a conversion gain of -6 dB and demonstrated a bandwidth of 44 GHz centered around 90 GHz for the IF input and 49 GHz centered around 216 GHz for the LO input. The mixer showed a 1 dB output referred compression point of -17.4 dBm, with a saturation power of -12 dBm.

Although not all mixer metrics were optimized to their fullest potential, the work successfully pinpointed the main factors limiting performance, primarily the losses associated with the transformers in the signal path. Future optimization efforts will concentrate on refining the layout and exploring alternative topologies to mitigate these losses and enhance the mixer's overall performance.