filter and fig2 b is a bottom plan view as shown in this figure for each of the inner conductor formed holes 2 a and 2 b a step is provided with respect to the center axis at the depth from the open face of l o so that the resonator pitch distance between the center axes of the inner conductor formed holes on the open face side is p o and the resonator pitch on the short circuiting face side is ps the inner diameters of the inner conductor formed holes 2 a and 2 b are constant over the range from the open face to the short circuiting face and is represented by d fig3 illustrates the results the q o of a resonator which is changed with the ratio of the width d inner diameter of an inner conductor formed hole formed coaxially in a dielectric block to the width d in the longitudinal and transverse directions of the dielectric block and is determined by the finite element method as seen in the results in the d d range of 0 2 0 4 the q o have a large value when the d d is 0 3 the q o becomes maximum the q.