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

Cui, Wenpu; Cui, Jie; Zhang, Wenchao; Yu, Guofang; Zhao, Di; Du, Jingqing; Li, Zhen; Fu, Jun; Ren, Tianling

doi:10.3390/mi16101151

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

by

Wenpu Cui

¹

,

Jie Cui

¹,

Wenchao Zhang

¹,

Guofang Yu

^1,2,

Di Zhao

³,

Jingqing Du

³,

Zhen Li

^1,*,

Jun Fu

^1,* and

Tianling Ren

^1,*

¹

School of Integrated Circuits and Beijing National Research Center for Information Science and Technology (BNRist), Tsinghua University, Beijing 100084, China

²

College of Computer Science and Technology, National University of Defense Technology, Changsha 410073, China

³

Beijing Sevenstar Flow Co., Ltd., Beijing 100176, China

^*

Authors to whom correspondence should be addressed.

Micromachines 2025, 16(10), 1151; https://doi.org/10.3390/mi16101151

Submission received: 4 September 2025 / Revised: 2 October 2025 / Accepted: 4 October 2025 / Published: 10 October 2025

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Abstract

This paper presents a thermal gas flow sensing system, from surface acoustic wave (SAW) temperature sensor to oscillation circuit and multi-module miniaturization integration. A single-port GaN/Si SAW resonator with single resonant mode and excellent characteristics was fabricated. Combined with an in-house-developed SiGe HBT, a temperature-sensitive high-frequency oscillator was constructed. Under constant temperature control, system-level flow measurement was achieved through dual-oscillation configuration and modular integration. The fabricated SAW device shows a temperature coefficient of frequency (TCF) −28.29 ppm/K and temperature linearity 0.998. The oscillator operates at 1.91 GHz with phase noise of −97.72/−118.62 dBc/Hz at 10/100 kHz offsets. The system demonstrates excellent dynamic response and repeatability, directly measuring 0–50 sccm flows. For higher flows (>50 sccm), a shunt technique extends the test range based on the 0–10 sccm linear region, where response time is <1 s with error <0.9%. Non-contact operation ensures high stability and long lifespan. The sensor shows outstanding performance and broad application prospects in flow measurement.

Keywords: SAW; thermal; GaN; gas flow sensor; SiGe HBT

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MDPI and ACS Style

Cui, W.; Cui, J.; Zhang, W.; Yu, G.; Zhao, D.; Du, J.; Li, Z.; Fu, J.; Ren, T. Thermal Gas Flow Sensor Using SiGe HBT Oscillators Based on GaN/Si SAW Resonators. Micromachines 2025, 16, 1151. https://doi.org/10.3390/mi16101151

AMA Style

Cui W, Cui J, Zhang W, Yu G, Zhao D, Du J, Li Z, Fu J, Ren T. Thermal Gas Flow Sensor Using SiGe HBT Oscillators Based on GaN/Si SAW Resonators. Micromachines. 2025; 16(10):1151. https://doi.org/10.3390/mi16101151

Chicago/Turabian Style

Cui, Wenpu, Jie Cui, Wenchao Zhang, Guofang Yu, Di Zhao, Jingqing Du, Zhen Li, Jun Fu, and Tianling Ren. 2025. "Thermal Gas Flow Sensor Using SiGe HBT Oscillators Based on GaN/Si SAW Resonators" Micromachines 16, no. 10: 1151. https://doi.org/10.3390/mi16101151

APA Style

Cui, W., Cui, J., Zhang, W., Yu, G., Zhao, D., Du, J., Li, Z., Fu, J., & Ren, T. (2025). Thermal Gas Flow Sensor Using SiGe HBT Oscillators Based on GaN/Si SAW Resonators. Micromachines, 16(10), 1151. https://doi.org/10.3390/mi16101151

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

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