A Battery-Operated Wireless Multichannel Gas Sensor System Based on a Capacitive Micromachined Ultrasonic Transducer (CMUT) Array

This paper reports on the design and implementation of a complete battery-operated wireless system for a mechanically resonant gas sensor based on a capacitive micromachined ultrasonic transducer (CMUT) array. A custom-designed front-end integrated circuit (IC) with eight inputs and a serial peripheral interface (SPI) was tightly integrated with a CMUT array. The power consumption of the front-end is 10 W with a duty cycle of 1:60 corresponding to 1-s measurement time every minute. For the completeness of the system, a power management unit (PMU) was designed and interfaced with the described custom IC along with a wireless module. For multichannel operation, time-division multiplexing was adopted to minimize power consumption and prevent potential frequency locking between different channels. Multichannel wireless data acquisition with the described system was demonstrated by loading unfunctionalized sensor channels with humidity in human breath.