| 摘要 |
Devices and methods to generate a mono-directional ultrasonic wave are provided. An ultrasonic sensor configured to emit a substantially mono-directional ultrasonic wave includes a first piezoelectric element and a second piezoelectric element. The first piezoelectric element is configured to generate a first ultrasonic wave propagating in a first direction and a second ultrasonic wave propagating in a second direction which is different from the first direction. The second piezoelectric element is located and configured to absorb the second ultrasonic wave, and is configured to convert an energy of the absorbed second ultrasonic wave into an electrical energy. |
