A mass-loading effect LiNbO/sub 3/ SAW sensor

A mass-loading effect SAW sensor with a quadrate (3mm/spl times/3mm) mass-loading effect groove is presented. Its input and output IDTs have 40 pairs and 60 pairs of aluminum electrodes respectively. A photoresist layer is covered on the surface of LiNbO/sub 3/ substrate to protect the aluminum electrodes and to construct the quadrate groove in the center of the sonic path. The tiny loading mass in this groove leads into a tiny center frequency shift of the SAW sensor. The loading mass density can be obtained from the frequency shift and the sensitivity curve. This kind of SAW mass-loading effect sensor can be used in direct measurement and dual SAW sonic path comparative measurement. The input and output IDTs can be worked in direct mode and oscillator mode connected with a high gain wide band amplifier. The testing results show that this mass-loading effect sensor possesses a better sensitivity (S=21.2ng/ppm*cm/sup 2/ in direct sensing and S=3.82ng/ppm*cm/sup 2/ in comparative sensing) and a higher linearity (/spl delta/ = /spl Delta//Sav = 3.1%) than the previous report[3].