This study was conducted to expand the measurement
range of a CWUA that determines velocity and direction
of wind from the change in the phase differences between
the receivers. When 40 kHz ultrasonic waves are used, the
actually measurable phase difference is limited to around
10 ls due to offset phase difference. In this study, a frequency
divider was used to decrease the frequency of the
received signals and the measurable phase difference
range was expanded, and the offset phase differences were
removed with a phase delay circuit. A receiving circuit was
designed to extend the measurable phase difference to
50 ls by using a phase delay circuit and a 1/4-frequency
divider. Furthermore, to solve the problem of the instant
shifting of the receiving waveform for a specific cycle when
the phase difference between the two asynchronous signals
that had passed the frequency divider was measured,
an algorithm for determining the validity of the measured
phase difference by comparing it with the previous value
was applied. It was found from the experiment that when
the proposed receiving circuit and algorithm are used, a
wind velocity of up to 60.96 m/s could be measured at a
maximum error of ±5%.