PURPOSE: To attain a filter of broad band, by combining a resonator of TEM mode and a resonator of TEO1δ mode suitable for broad band comparatively.

CONSTITUTION: Resonance rods 13, 13 comprising conductors are connected to a center conductor (not shown in figure) of coaxial plugs 12, 12 with connection conductors 15, 15. The resonance rods 13, 13 are resonated in the TEM mode together with a case 11 and its Qe depends on a distance (l) from the connection conductor 15 to the case 11. Further, the characteristics of the resonators 14, 14 of the TEO1δ mode the same as those using a ceramic dielectric. In this way, the ratio of the band width BW to a center frequency fO, (BW/fO)×100 is extended, e.g. from 2% to 10% by adjusting said distance (l).