In conventional ultrasonic pulse-echo sensing,
accurate target bearing measurement is often
regarded as difficult due to the wide beam angle of ultrasonic transducers.
However, measurement of the accurate angle
is also very useful for many robot motions.
One method of satisfying this requirement is using a single transmitter
and multiple receivers with time-of-flight.
In this system, a much wider directivity is required for measuring
a much wider area.
In this paper, a multiple transmitter system is suggested for getting
a much wider directivity.
A fundamental experiment on the multiple transmitter and multiple receiver
system is also described.