Surface Acoustic Wave Filter

A Surface Acoustic Wave (SAW) filter is a filter whereby the electrical input signal is converted to an acoustic wave by so-called interdigital transducers (IDTs) on a piezoelectric substrate such as quartz or LiNbO₃.  The IDTs consist of interleaved metal electrodes, which are used to launch and receive the waves, such that an electrical signal is converted to an acoustic wave and then back to an electrical signal.

The most common group of SAW-filters is band pass filters, which are in very widespread use in radio systems (including mobile phone handsets and base stations) and in CATV.  There are many types with different advantages, such as low shape factor, low insertion loss, small size, or high-frequency operation.  The wide variety of types is possible because almost arbitrary shapes can be defined on the piezoelectric substrate surface with very high precision.

SAW filters are limited to frequencies from about 50MHz up to 3GHz.