Ends of the tegular filters (10) are cut off crosswise to make the end surfaces respectively form inclined surfaces such that vertical sections of the tegular filters (10) are in a rough trapezoid.

瓦状滤波器(10)的端部被斜向切除以使端面分别形成斜面，从而瓦状滤波器(10)的垂直截面呈大致梯形。