Transmission Mediums : Surface Acoustic Wave (SAW)

A surface acoustic wave (SAW) involves the mechanical transmission of a wave that travels on the surface of a material. The wave is created by a piezoelectric transducer that converts electrical to acoustic energy into mechanical vibrations that are coupled (connected) to a material that allows the wave to propagate across the surface of the material. A second transducer (e.g., a pattern of metal fingers) converts the acoustic energy back into an electrical form. Depending on the shape and type of material for which the SAW travels, the signal characteristics can be changed (such as the passing or rejecting of particular frequency bands).

A fundamental use of a SAW device is to act as a signal delay line. The relatively slow propagation velocity of the surface acoustic waves of typically 3500 m/s allows delays of several microseconds on a small chip[1]. There are many variations of SAW technology including delay lines, filters, resonators, pulse compressors, convolvers, and many more.

The first SAW devices were introduced to the marketplace in the mid-1960’s. Before the year 2000, more than 5 million surface acoustic wave (SAW) devices were being installed in electronics assemblies each day[2].

Figure below shows a transmission system that uses surface acoustic wave (SAW) technology. This device is a radio frequency filter that uses SAW technology. The radio signal is applied to an IDT. The IDT converts the electrical signal to an acoustic (mechanical) wave that moves across the surface of the SAW filter substrate. When the acoustic wave reaches the destination IDT, it is converted back into an electrical signal.


Surface Acoustic Wave (SAW) Transmission