Thermal Gas Flow Sensor Using SiGe HBT Oscillators Based on GaN/Si SAW Resonators

Area of Science:

• Materials Science
• Electrical Engineering
• Sensor Technology

Background:

• Accurate gas flow measurement is crucial in various industrial applications.
• Existing flow sensors often face limitations in terms of accuracy, response time, or lifespan.
• Miniaturization and integration of sensing components are key trends in modern sensor development.

Purpose of the Study:

• To develop and present a miniaturized, integrated thermal gas flow sensing system.
• To utilize a surface acoustic wave (SAW) temperature sensor for precise temperature monitoring within the flow system.
• To achieve high-performance, non-contact gas flow measurement.

Main Methods:

• Fabrication of a single-port Gallium Nitride on Silicon (GaN/Si) SAW resonator.
• Construction of a temperature-sensitive high-frequency oscillator using a Silicon-Germanium Heterojunction Bipolar Transistor (SiGe HBT).
• Implementation of a dual-oscillation configuration and modular integration for system-level flow measurement.

Main Results:

• The SAW device exhibited a temperature coefficient of frequency (TCF) of -28.29 ppm/K with high linearity (0.998).
• The oscillator operated at 1.91 GHz with good phase noise characteristics.
• The system demonstrated accurate measurement of 0-50 standard cubic centimeters per minute (sccm) flows with <1 s response time and <0.9% error, extendable to higher ranges using a shunt technique.

Conclusions:

• The developed thermal gas flow sensing system offers high stability, long lifespan, and excellent performance.
• The non-contact operation and modular design ensure broad application prospects in gas flow measurement.
• The integration of SAW resonator and SiGe HBT oscillator provides a robust platform for advanced flow sensing.