Abstract: A multi-band array antenna comprises m first antenna elements operating in p frequency bands; n second antenna elements operating in q frequency bands; a Wilkinson power distributor; one or more filters; and one or more matching circuits. Here, m and n are positive integers satisfying m+n?3 and any of m=n+1, n=m+1 and m=n; and p and q are positive integers satisfying p?1, q?2 and q>p. The m first antenna elements and the n second antenna elements are alternately arranged. The matching circuit performs impedance matching between the filter and the Wilkinson power distributor in a frequency band attenuated by the filter. A series-connection circuit portion is configured so that a branch portion of the power distributor becomes an open end in the attenuation frequency band.

Abstract: A multi-band array antenna comprises m first antenna elements operating in p frequency bands; n second antenna elements operating in q frequency bands; a Wilkinson power distributor; one or more filters; and one or more matching circuits. Here, m and n are positive integers satisfying m+n?3 and any of m=n+1, n=m+1 and m=n; and p and q are positive integers satisfying p?1, q?2 and q>p. The m first antenna elements and the n second antenna elements are alternately arranged. The matching circuit performs impedance matching between the filter and the Wilkinson power distributor in a frequency band attenuated by the filter. A series-connection circuit portion is configured so that a branch portion of the power distributor becomes an open end in the attenuation frequency band.

Abstract: The gap-providing ferrite core half is produced by grinding an abutting surface of a ferrite core half by a rotating grinder with a rotation shaft inclined by 0.

Abstract: The gap-providing ferrite core half is produced by grinding an abutting surface of a ferrite core half by a rotating grinder with a rotation shaft inclined by 0.1.degree.-45.degree. relative to a line vertical to a surface of the ferrite core half to be ground in a plane parallel to a core width direction, so that the resultant gap-providing recess is constituted by a concave elliptical plane expressed by the following formula: ##EQU1## wherein A is a width of the ferrite core half, R is an effective radius of the grinder, .theta. is an inclination angle of the rotation shaft of the grinder relative to a line vertical to a surface of the ferrite core half to be ground, and G is a gap depth.