Methods of distinguishing among touch events using piezoelectric micromechanical sensing

A method of distinguishing between a first-type touch event and a second-type touch event at a sense region, the method comprising:

• configuring a system at the sense region, the system comprising:
• at least one piezoelectric micromechanical force-measuring element (PMFE), each PMFE comprising a respective piezoelectric capacitor;
• and
• at least one piezoelectric micromechanical ultrasonic transducer (PMUT), each PMUT comprising a respective piezoelectric capacitor, each PMUT being configured as a PMUT transmitter and/or a PMUT receiver, the PMUT transmitter(s) numbering at least one, and the PMUT receiver(s) numbering at least one;
• transmitting, by each PMUT transmitter, ultrasound signals of a frequency F1, in longitudinal mode(s) propagating along a direction approximately normal to a plane of the respective piezoelectric capacitor towards the sense region;
• reading, by a signal processing circuitry, voltage signals from the PMUT receiver(s) generated in response to ultrasound signals of the frequency F1 arriving at the PMUT receiver(s) from the sense region;
• reading, by the signal processing circuitry, voltage signals from the PMFE(s) generated in response to a low-frequency mechanical deformation of the respective piezoelectric capacitor(s);
• processing the voltage signals from the PMUT receiver(s) to obtain PMUT digital data;
• processing the voltage signals from the PMFE(s) to obtain PMFE digital data;
• determining that an event at the sense region is the first-type touch event if (1a) the PMUT digital data decrease by at least a minimum decrease percentage of a predetermined dynamic range in a moving time window of a predetermined duration, and (2a) a magnitude of the PMFE digital data is greater than a PMFE threshold value;
• and
• determining that the event is the second-type touch event if (1a) the PMUT digital data decrease by at least the minimum decrease percentage of the predetermined dynamic range in the moving time window of the predetermined duration, and (2b) the magnitude of the PMFE digital data is not greater than the PMFE threshold value,
• wherein:
• the first-type touch event comprises a first object contacting the sense region and the second-type touch event comprises a second object contacting the sense region.