Design and analysis of a novel SAW sensor for civil structural health monitoring

ABSTRACT

This paper presents a novel surface acoustic wave sensor for civil structural health monitoring. The sensing chip packaged in a shell is composed of two SAW delay line dice. One is utilized to sense the pressure induced by a gauge, and the other is used to sense the surrounding temperature for temperature compensation. Each SAW delay line die consists of an inter-digital transducer and two open grating reflectors. The SAW devices are analyzed by using coupling of modes model. Then, the devices in different parameters are fabricated on a 128°Y-X cut LiNbO₃ substrate by lift-off technique. Finally, a network analyzer is utilized to test the devices. Large signal-to-noise ratio, low loss and clear sharp peaks of the reflection coefficients S₁₁ in frequency and time domain can be observed. The experimental results matched well with the theoretical analysis by the finite element software COMSOL. The IDT finger pairs number, electrodes number of per reflector and acoustic aperture effect the reflection coefficient S₁₁ is discussed in detail.

KEYWORDS:

• Surface acoustic wave
• delay line
• inter-digital transducer
• coupling of modes

Funding

The authors wish to thank support from the National Natural Science Foundation of China (Grant no. 51505499) and the Jiangsu Province Natural Science Foundation of China (Grant no. BK20150712).