Title :
Simultaneous and wireless measurement of CO2 and NO2 using a saw reflective delay line
Author :
Lim, Chunbae ; Yang, Sangsik ; Lee, Keekeun
Author_Institution :
Dept. of Electron. Eng., Ajou Univ., Suwon, South Korea
Abstract :
A 440 MHz wireless and passive surface acoustic wave (SAW) based micro-sensor was developed on a 41deg YX LiNbO3 piezoelectric substrate for simultaneous measurement of CO2 and NO2. The developed sensor consists of a SAW reflective delay lines structured by an interdigital transducer (IDT), ten reflectors, CO2 sensitive film (Teflon AF 2400), and NO2 sensitive film (Indium Tin Oxide). The coupling of mode (COM) modeling was conducted to determine optimal device parameters prior to fabrication. According to simulation results, the device was fabricated and then wirelessly measured using the network analyzer. The measured reflective coefficient S11 in the time domain showed high signal/noise (S/N) ratio, small signal attenuation, and few spurious peaks. From the experimental results, high selectivity and sensitivity were observed in each concentration of gases. The obtained sensitivity was 2.12deg/ppm for CO2 and 55.4deg/ppm for NO2. Temperature compensation was performed during sensitivity evaluation process.
Keywords :
carbon compounds; gas sensors; interdigital transducers; lithium compounds; microsensors; network analysers; nitrogen compounds; piezoelectric devices; surface acoustic wave delay lines; surface acoustic wave sensors; CO2; LiNbO3; NO2; SAW reflective delay line; SAW sensor; coupling-of-mode modeling; gas sensor; interdigital transducer; microsensor; network analyzer; piezoelectric sensor; reflective coefficient; sensitivity evaluation process; temperature compensation; wireless measurement; Acoustic measurements; Acoustic sensors; Acoustic waves; Delay lines; Gas detectors; Optical films; Piezoelectric transducers; Substrates; Surface acoustic waves; Wireless sensor networks; Batteryless; CO2; NO2; SAW (surface acoustic wave); multi-gas sensor; reflective delay line; wireless;
Conference_Titel :
Solid-State Sensors, Actuators and Microsystems Conference, 2009. TRANSDUCERS 2009. International
Conference_Location :
Denver, CO
Print_ISBN :
978-1-4244-4190-7
Electronic_ISBN :
978-1-4244-4193-8
DOI :
10.1109/SENSOR.2009.5285955
