Patent attributes
A touch sensor includes: a transmitter configured to transmit an ultrasonic transmit wave towards a touch structure; a receiver configured to receive an ultrasonic reflected wave produced from the ultrasonic transmit signal being at least partially reflecting by the touch structure; a receiver circuit configured to convert the ultrasonic reflected wave into a measurement signal; the receiver circuit configured to generate an error value representative of a difference between a measured value of the measurement signal and a reference value; a programmable voltage source configured to provide a bias voltage to the transmitter or to the receiver; a controller configured to adjust the bias voltage based on the error value; a measurement circuit configured to measure the DC bias voltage and determine whether a no-touch event or a touch event has occurred at the touch structure based on at least one measurement of the bias voltage.
