An ultrasonic rangefinder based on an AlN piezoelectric micromachined ultrasound transducer

An ultrasonic rangefinder has a working range of 30 mm to 450 mm and operates at a 375 Hz maximum sampling rate. The worst-case systematic error less than 1.1mm. The rms noise is proportional to the square of the 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 consisting of a piezoelectric AlN membrane with 400 μm diameter which was fabricated using a low-temperature process compatible with processed CMOS wafers. All circuits are low voltage, enabling integration in standard low voltage circuit technology.