Investigation of single-finger interdigital transducer as programmable reflector

In the last decade, the split-finger interdigital transducer (IDT) was proposed to be used as a programmable reflector because it is well-known that the reflection coefficient of split-finger IDT when short circuited is very small. Thanks to this intriguing property, the split-finger IDT was frequently used in wirelessly passive surface acoustic wave (SAW) identification systems and sensors. In this paper, the single-finger IDT used as programmable reflector was investigated. The periodic structures printed on a 128°YX-LiNbO₃ substrate show an extraordinary characteristic: for a certain ratio of electrode height and wavelength, the reflection of a short-circuited (SC) grating almost disappears. On the contrary, the reflection of an open-circuited (OC) grating is big. Therefore, the single-finger interdigital transducer can be used as programmable reflector. The amplitude modulation is great enough. The height/wavelength dependence of amplitude modulation has been simulated. The results of real devices were compared with those of the simulation. If using single-finger IDT instead of split-finger IDT, the working frequency is twice the amount when using the technology with the same resolution.