We propose a nanocrystalline porous silicon (nc-PS) ultrasonic transmitter with a controllable directional pattern. The directional pattern is realized by using an interference effect. An ultrasonic wave is emitted from electrodes on the nc-PS layer. The emission areas of the transmitter were patterned in order to use the interference between the emitted ultrasonic waves. To observe the interference effect, our device was designed to have two emission areas. The direction of the main lobe was variable from about -30 to 30 degrees. With the characteristics of the controllable directional pattern, the proposed device is suitable for distance sensors, especially for proximity sensors.

References :
Akihiro Isozaki, Akihito Nakai, Kiyoshi Matsumoto, Isao Shimoyama, “Nanocrystalline Porous Silicon Ultrasonic Transmitter with Patterned Emission Area,” 20th IEEE International Conference on Micro Electro Mechanical Systems (MEMS '07), pp. 55-58, Kobe, Japan, Jan. 21-25, 2007. Proceedings