Abstract: A circuit for an acoustic wave switch or sensor having a resonant acoustic wave cavity detects a touch or sensed event using a time domain approach. The circuit includes a controller that drives an acoustic wave transducer to generate a resonant acoustic wave in the acoustic wave cavity during a first portion of a sampling cycle. In a second portion of the sampling cycle, the controller monitors the time that it takes for the acoustic wave signal from the transducer to decay to a predetermined level. Based on the decay time, the controller detects a sensed event, such as a touch on the acoustic wave switch/sensor.

Abstract: Certain embodiments provide an acoustic wave touch bar system and method of use. Certain embodiments include a bar having two portions of reduced cross-section forming an acoustic cavity in the portion of the bar between the reduced cross-sections. The system includes an acoustic wave transducer positioned on the acoustic wave cavity, wherein the transducer generates an acoustic standing wave that is substantially trapped in the acoustic cavity. The system also includes a circuit coupled to the transducer and responsive to a change in an output of the transducer to detect a touch on a touch surface of the bar. The circuit may be a programmable and/or adaptive circuit, for example. The circuit may detect a change in an exponentially decaying response of the transducer indicating that the touch surface of the bar has been touched.

Abstract: An acoustic wave sensor utilizes one or more acoustic waves trapped in an acoustic wave cavity to detect the presence of one or more substances on a surface of the acoustic wave cavity. To detect the presence of ice, a trapped torsional acoustic wave is used. To detect water, an acoustic wave with flexural or compressional components is used. The sensor includes a number of transducers adjacent the acoustic wave cavity where a controller drives different sets of the transducers to generate different acoustic waves.

Abstract: An acoustic wave sensor/resonator utilizes a torsional wave trapped in an acoustic wave cavity that is formed in a noncylindrical substrate. An acoustic wave transducer is positioned adjacent the acoustic wave cavity off of the centerline of the cavity and in a plane parallel to a planar surface of the acoustic wave cavity to generate the torsional wave. The acoustic wave transducer can be a piezoelectric transducer or an electromagnetic transducer. Further, the torsional wave can be generated by a single transducer or multiple transducers.