Ultrasonic touch detection and decision

A method performed by a touch sensor chip comprising an ultrasound sensor layer including an array of ultrasonic transducers and an integrated circuit layer coupled to the ultrasound sensor layer, wherein the array of ultrasonic transducers comprises a transmitting set of ultrasonic transducers configured for transmitting ultrasound signals and a receiving set of ultrasonic transducers configured for receiving ultrasound reflections associated with transmitted ultrasound signals, wherein the transmitting set of ultrasonic transducers are separate from the receiving set of ultrasonic transducers, the method comprising:

• generating a driving signal in the integrated circuit layer coupled to a transmitting ultrasonic transducer in the array of ultrasonic transducers coupled to the integrated circuit layer;
• generating an emitted ultrasound signal, by the transmitting ultrasonic transducer, in response to the driving signal, wherein generating the emitted ultrasound signal comprises transmitting the emitted ultrasound signal through a material layer in a longitudinal direction that is normal to an exterior surface of the material layer;
• receiving a set of reflection signals at a receiving ultrasonic transducer in the array of ultrasonic transducers, wherein the set of reflection signals comprise one or more ultrasound signals associated with the emitted ultrasound signal;
• measuring an energy signal associated with the received set of reflection signals;
• and
• determining that a touch event has occurred at the exterior surface of the material layer based on the measured energy signal.