Many cell phones use a high frequency (RF) filter that suppresses interference and passes only the signal wave. These RF filters need to be compact, thin, and inexpensive for use in cell phones, as well as have good filter breakup and low loss characteristics for effective use of radio waves. For this reason, SAW filters are currently being used in most cell phones.
Surface Acoustic Wave (SAW) is a wave that propagates on the surface of a material, and SAW filters are filters that use this characteristic. By taking advantage of its compact size and light weight, the SAW filter contributes to the development of the mobile communication market and the development of compact, high performance, and multi-function handsets.
In the SAW filter, as shown in Fig.1, the input of a high-frequency electrical signal is converted into a surface wave of several microns in length by the piezoelectric effect of a piezoelectric substrate, and the surface wave is propagated on the piezoelectric substrate, filtered to the desired frequency, and then extracted as an electrical signal again.
To prevent the free vibration of surface waves, a cavity-preventing structure similar to MEMS is required, and package structures such as the one shown in Fig. 2 are often used. We provide the materials to form this structure, which is used by a variety of customers due to its high reliability.
TMMF＆TMMR in the text is a pending or registered trademark of TOK.
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