Abstract
We present a new method for surface acoustic wave (SAW) sensing which overcomes the main disadvantages of the well-known dual-delay-line oscillators, namely the insufficient sensitivity for atmospheric measurements and the strong temperature-dependent drift of the output frequency signal. Our method is based on the reflection of a SAW by a periodic array. SAW reflection occurs at discontinuities of the surface. If these discontinuities vary with the presence of the substance to be detected, the reflection coefficient of the array, and thus the amplitude of the reflected SAW, changes. With this method we have reached a sensitivity of 0.3 ppb for NO 2 with a 370 MHz device on a LiNbO 3 substrate.
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