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Surface Acoustic Wave Device

The next device we examined we examined was a Surface Acoustic Wave (SAW) device. This is a device used to pick out a particular frequency of wave, and damp out all the other frequencies, so only the desired frequency, and no other background waves are picked up. They are used in mobile phones as they are cheaper, smaller and are better than other alterantives such as quartz crystal.


The SAW device under an optical microscope.

These devices work by mechanical oscillating up and down at the freqency of the desired wave. At this frequency, it can pick up the wave, but other frequencies get absorbed out of the wave, anso you could get a wave at a desired frequency. Below is a picture of the device taken with an optical microscope from an angle, and it shows different coloured lines of the transducers, which highlights the different spacing between the electrodes, which corresponds to different frequencies of the wave.

SAW colour

SAW device highlighting different electrode spacings.

The picture below shows buffers at the end of the transducers, which are not connected to the rest of the transducer. These damp out the wave at at the end to stop it continuing.

SAW 100x

Zoomed image of the electrodes, with the ones on the right not connected, to damp out the wave.

This lack of connection is hgihlighted in the picture below, which was taken in the SEM, where we can see the buffers on the end charging up because they are not connected to the rest of the device.

SAW charging

The buffers on the right are charging much quicker than the rest of the SAW.