The surface acoustic wave (SAW) device has been used in many applications, such as using as resonators, to replace the inductance-capacitance (LC) filters, chemical or gas sensors. Our objectives in this work are to increase insertion loss (IL) and Q factor. The new improved device has applications in RF engineering as well as in sensors. They are used to sense the additional particles on the surface, which have a good potential for biological sensors.;In this work, a synchronous low-loss one-pole SAW resonator is designed to improve the existing SAW filter design. The mass-sensing applications of SAW resonators indicate the different potential for applications in biosensors. There are three objectives studied in this work. The first objective is to develop a low-loss and one-pole frequency response for SAW resonators. The insertion loss, which is the receiving power in the output transducer, is typically smaller than -6dB. Our goal is to achieve a low-loss response (>-3dB), and then it is necessary to improve the performance of SAW as a filter and as a biosensor. The bidirectional SAW resonator on the LiNbO3 piezoelectric substrate have two-pole frequency response and low a Q factor. An improved frequency response with high Q factor is introduced in this work. The second objective in this research is to develop a SAW mass sensor on the LiNbO 3 substrate. When the additional mass is deposited on the surface, it results in a decrease in velocity and center frequency of acoustic waves. This decrease of the center frequency, or frequency shift, is linearly related to the additional mass. A frequency shift, due to the additional mass, can be observed by the low-loss and one-pole response in the output. This mechanism allows a synchronous low-loss one-pole SAW resonator to have potential application in sensors; however, it is easier to determine the frequency shifts if the SAW resonator has a one-pole response in the output interdigital transducer (IDT). The mass sensitivity in this work is 8.23e12 Hz˙mm 2/g for 978MHz SAW mass sensor. The third objective in this work is to use the SAW mass sensor operational in a liquid-phase environment for mass detection. The acoustic waves are excited by conductive electrodes on the piezoelectric surface; the signal on these electrodes becomes shorted when the SAW device is in liquid. In order to protect the electrodes, a polymer coating is applied to the surface in order to avoid the short circuit. This polymer-coated SAW mass sensor makes it possible to sense antibody-antigen reactions in liquid.
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