The ultrasonic signals that were inputted through the
ultrasonic receiver are sine wave signals that have several
tens of mV of noise. The previous receiving circuit of CWUA
amplifies and filters such sine waves, and converts them
into 5 V TTL signals that are appropriate for phase difference
measurement in the microcontroller. In this study,
to expand the measurement range, a phase delay circuit
was inserted in front of the comparator, as shown in