In-Air Rangefinding With an AlN Piezoelectric Micromachined Ultrasound Transducer

An ultrasonic rangefinder has a working range of 30 to 450 mm and operates at a 375-Hz maximum sampling rate. The random noise increases with distance and equals 1.3 mm at the maximum range. The range measurement principle is based on pulse-echo time-of-flight measurement using a single transducer for transmit and receive. The transducer consists of a piezoelectric AlN membrane with 400-μm diameter, which was fabricated using a low-temperature process compatible with processed CMOS wafers. The performance of the system exceeds the performance of other micromechanical rangefinders.