US Patent 11934617 Ultrasonic touch sensor using capacitive cross-talk

A touch sensor includes a touch structure; a signal generator configured to generate an excitation signal; a transmitter configured to receive the excitation signal and transmit an ultrasonic transmit wave towards the touch structure based on the excitation signal; a receiver configured to receive an ultrasonic reflected wave produced by a reflection of the ultrasonic transmit wave at the touch structure, wherein the transmitter and the receiver are coupled by a capacitive path, the receiver is configured to be influenced by the excitation signal whereby the excitation signal induces a capacitive cross-talk on the capacitive path, and the receiver is configured to generate a measurement signal representative of the capacitive cross-talk; and a measurement circuit coupled to the receiver and configured to perform a comparison of the measurement signal with a threshold to determine whether a no-touch event or a touch event has occurred at the touch interface.