A surface acoustic wave, namely SAW, is an acoustic wave traveling along the surface of a material. Accordingly, a SAW device is designed to make use of SAWs to process electrical signals in an analog way, and its frequency range is about 30MHz~2400MHz. At SJK, several SAW filters and SAW resonators are provided.
Structure
As a kind of electronic component, our surface acoustic wave device is mainly composed of a piezoelectric substrate (or materials with piezoelectric effect) and one or more interdigital transducers (IDTs). These IDTs consist of a series of interleaved electrodes which are made of metal films, and they are deposited on the polished surface of the substrate.
Technically speaking, several kinds of materials have been adopted to fabricate the substrate. For example, some piezoelectric single crystals, including quartz, lithium niobate, bismuth germinate and lithium tantalite, are commonly utilized, while Z-axis oriented zinc oxide film could be deposited on non-piezoelectric materials, such as glass, to make the substrate as well. In addition, piezoelectric ceramics are also applicable for low frequency use.
Advantage
1. High energy density: For our SAW device, wave energy decays exponentially away from substrate surface, so that about 90 percent of wave energy is confined within a depth equal to one wavelength.
2. Low propagation velocity: Under most conditions, SAW travels at a speed range of 3000~5000m/s, which is about 45% of that of longitudinal waves, and 90% of that of transverse waves.
Performance
1. SAW is characterized by ultra low propagation velocity and super short wave length, which are 100 thousand times smaller than those of electromagnetic waves. But SAW devices sometimes perform much better than even the best devices that use electromagnetic waves. For example, with the help of SAW, a resonant cavity, with Q factor of over 50,000 in UHF band, could be manufactured, and a bandpass filter, whose out-of-band rejection and center frequency are 70dB and 1GHz respectively, is also attainable.
2. Since SAW-based devices are manufactured via planar process, they exhibit good consistency and repeatability, thus facilitating mass production.
3. Our product shows good resistance to radiation, and its dynamic range could reach up to 100dB.
Application
Due to the outstanding properties of SAW devices, such as small size, light weight, flexible design, wide time domain, large dynamic range, excellent signal processing ability, ease of mass production and simple cooperation with external circuits, they are extensively used in commercial, industrial and military systems.
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