The ultrasonic anemometer is an indispensable measurement
equipment for accurate meteorological observations
[1,2]. The existing ultrasonic anemometers measure
the travel-time of ultrasonic waves and have high accuracy,
but they are expensive because they use high-frequency
sensors, have complex internal structures due to their
time-sharing method, and have a limitation in raising the
sampling rate [3–8].
To address these demerits, a continuous wave ultrasonic
anemometer (CWUA) was proposed that determines
the velocity and direction of wind by measuring the phase
difference between the ultrasonic signals that are received
through multiple-receivers within the transmitting range
while the transmitter continuously transmits ultrasonic
waves [9].
Since the CWUA measures only the phase difference between
the ultrasonic waves that are received through the
receivers, its transmitting unit and receiving unit are completely
separated, which simplifies its internal structure.