550 GHz Band GaAs Thin-film Integrated Mixer Technology for Space Exploration Applications

The Terahertz (THz) frequency band offers unique application prospects in cutting-edge fields such as space exploration, planetary atmospheres, radio astronomy, and inter-satellite communications. THz solid-state Schottky harmonic mixing technology is a crucial technique that can down-convert THz signals to the microwave band for high-speed signal processing. It is evident that research on THz monolithic integrated harmonic mixers holds significant importance, as it effectively overcomes the inherent limitations of conventional hybrid integration approaches (e.g., epoxy-bonded discrete Schottky diodes with quartz matching circuits), including assembly complexity, thermal imbalance effects, and compromised reliability. Alternatively, the 550 GHz spectral band, as a molecular fingerprint region for water, plays an indispensable role in space-based detection applications. In this paper, the development and verification of a 550 GHz-band monolithic integrated harmonic mixer has been successfully completed based on a fully domestic GaAs foundry process line. The main technical contributions include: For diode design, building upon planar Schottky diode architectures developed by Jet Propulsion Laboratory (JPL) and France’s LERMA laboratory, the accurate nonlinear and 3D models of Schottky varactor diodes tailored to domestic fabrication processes are established. For matching circuit, it employs a canonical reduced-height waveguide coupled with high-low impedance suspended microstrip lines (for RF-LO isolation) and rectangular probe structures, achieving an optimized matching network through field-circuit co-simulation methodology. For monolithic integration, the complete frequency multiplier circuit, comprising diode pairs, matching networks, and probe structures, is monolithically integrated on a 3-μm-thick GaAs membrane with beam-lead interconnects on both sides, enabling robust cavity mounting. Test results demonstrate that the mixer module achieves a Single-Sideband (SSB) conversion loss of 11.7～13 dB across the 548～572 GHz RF frequency range, with a LO drive power of approximately 5 mW. Based on experimental characterization, this work systematically investigates the influence of series resistance R_s and zero-bias junction capacitance C_j0 variations on mixer performance, establishing a design feedback loop through correlated simulation-experimental analysis.