page_title: Surface acoustic wave sensor
section_title: Device Layout
hierarchical_section_title: Surface acoustic wave sensor / Device Layout
caption_attribution_description: English: General structure of a surface acoustic wave sensor with connections to an AC voltage source and a signal processing unit. In some sensors, the acoustic absorbers are replaced with reflectors to decrease insertion loss. A wireless surface acoustic wave sensor can be made by replacing the output IDT and coupling the input IDT to an radio-frequency (RF) antenna rather than a voltage source.
context_page_description: Surface acoustic wave sensors are a class of microelectromechanical systems which rely on the modulation of surface acoustic waves to sense a physical phenomenon. The sensor transduces an input electrical signal into a mechanical wave which, unlike an electrical signal, can be easily influenced by physical phenomena. The device then transduces this wave back into an electrical signal. Changes in amplitude, phase, frequency, or time-delay between the input and output electrical signals can be used to measure the presence of the desired phenomenon.
context_section_description: The basic surface acoustic wave device consists of a piezoelectric substrate with an input interdigitated transducer (IDT) on one side of the surface of the substrate, and an output IDT on the other side of the substrate.  The space between the IDTs across which the surface acoustic wave propagates is known as the delay line; the signal produced by the input IDT - a physical wave - moves much slower than its associated electromagnetic form, causing a measurable delay.
caption: Surface Acoustic Wave Sensor Interdigitated Transducer Diagram
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