High stable and sensitive orthogonal frequency coded SAW tags and sensors using unidirectional IDT and high coupling zero TCF substrates

Surface acoustic waves (SAWs) have been applied in various electronic devices, e.g., different kinds of filters, stable high frequency oscillators, real time signal processing devices, convolvers and matched filters used in spread spectrum communication systems. To obtain the high-performance surface acoustic wave (SAW) devices, it is very important for the high-coupling SAW materials and interdigital transducer (IDT) to be made unidirectional ones (UIDT). OFC is the use of orthogonal frequencies to encode a signal, which spreads the signal bandwidth in a manner similar to a fixed M-ary frequency shift signal. In this papers, we propose the new configuration of the internal reflection type of unidirectional IDT (λ/4 types) with the super high coupling substrates of SiO₂/YX-LiNbO₃ with k²=0.3 and zero Temperature Coefficient of Frequency (TCF). The above UIDT and substrates are applied to the low loss wide band filter, Tags and Sensors. The calculation results show the large wide-band width and very low insertion filters, tags and sensors without the degradation of the pulse response over the temperature by zero TCF substrates.