PURPOSE: To obtain a directivity angle which varies over a wide range at a specific frequency through simple constitution by uniting a center oscillator which consists of one or plural oscillators with plural outside oscillators.

CONSTITUTION: Sixteen oscillators 1 in a rectangular prism shape are adhered together in a square shape. Thus, the oscillator is constituted as mentioned above, and either or both of the center oscillator 2 and outside oscillators 3 are oscillated to obtain various directivity angles. In this case, the sixteen oscillators are used, but one oscillator 2 and eight oscillators 3 are usable, and more oscillators may be used. Each oscillator 1 may be a regular-hedron or have two facing surfaces which are diamond, polygonal, or circular.