The number of radio frequency surface acoustic wave (SAW) filters produced presently exceeds 3 billion per year. The demand for high-frequency SAW filters for telecommunications and remote sensing, has led to extensive research, focusing on new SAW microdevices. SAW devices have shown compact structures, small size, low cost, high sensitivity and fast response. The need of miniaturized systems, with high sensitivity and low energy has motivated the need to integrate on the same substrate all the structure of SAW device and connecting electronic circuits. As a consequence, many types of methods of both constructive and operating characterization of SAW devices have been developed. This paper provides a short introduction regarding the developed level of SAW microdevices and describes the results of literature investigation research of optoelectronic techniques for constructive characterization of SAW microdevices. Further research will be done into the determination of SAW parameters such as the amplitude of surface wave, the velocity of wave propagation on the surface of the piezoelectric substrate. Substrates of quartz, lithium tantalite (LiTaO 3 ) and lithium niobate (LiNbO 3 ), are piezoelectric materials commonly used in manufacturing of SAW devices, but these materials are not compatible with the integrated circuit (IC) technology. Three optoelectronic measurement techniques are known for detection of surface acoustic waves: diffraction grating technique, the knife-edge technique, and the detection of ultrasonic vibrations using optical interferometry. The research work given in this paper concentrates on describing of optoelectronic techniques used for constructive characterization of SAW microdevices. Finally, we try to draw some conclusion where: optoelectronic techniques are predicted to be one of the fundamental measurement methods for measurement of future SAW microdevices.
Between other sensing and identification technologies that of Surface Acoustic Waves, (SAW), is a unique sensing system. The principal advantage to most SAW systems is that they can use two or three SAW sensors and compare the measurements between them, providing a good accuracy. We have carried out the design of both piezoelectric substrate and inter.digital transducers, (IDTs), and has tested them in a delay line mode operation. The measurement of changes in the surface waves characteristics were materialized by applying of a radio frequency electric field to the piezoelectric crystal by means of IDTs. The finger width of the 1DTs was measured by high accuracy optical coherent method. The results are presented in the work. The potential development of microsensors as an array of four or five miniature sensors, sensitive to different chemicals may be used as mobile chemical detecting units carried by remote control vehicles to the site chemical contamination.
The results of research into Surface Acoustic Wave -SAW -devices have been recognized for their efficiency and versatility in the electrical signals processing [1], [3]. Actual progress in the industrial application of piezoelectric materials such as Lithium Niobate (LiNbO 3 ), Langasite (LGS), Lanthanum-Gallium Silicate La 3 Ga 5 SiO 14 and Gallium Orthophosphate (GaPO 4 ), allows the manufacturing of devices with performances, which overcome the limits obtained with quartz crystals [2]. The single crystal materials have a long term high stability -near to infinite -and moreover, some of these have an excellent behavior with temperature variation, as is the case of GaPO 4 [4]. Today, GaPO 4 with its properties is by far the best suited piezoelectric material to be used in sensor applications for machine monitoring and pressure measurements, at high temperatures. SAW microdevices based on GaPO 4 operate at temperatures of up to 800 0 C. We have developed five SAW filters based on GaPO 4 . The paper describes the steps to solve the problems regarding the use of GaPO 4 substrates for the development of SAW filters. In the 3rd chapter of the paper are given some experimental results obtained with Network Analyzer.
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