Electromagnetic frequency filter
The object of the present invention is to provide an electromagnetic wave frequency filter capable of transferring an electromagnetic wave having a prescribed frequency between two waveguides at high efficiency. To achieve the object, a resonator 15 which resonates to the electromagnetic wave having the prescribed frequency is arranged between an input waveguide 13 and an output waveguide 14 by being made to be close to both waveguides. The output waveguide 14 is made to be parallel with the input waveguide 13 in a prescribed extent 18 near the resonator 18 and is made so that the distance with the input waveguide 13 becomes longer than that in the prescribed extent 18 in extents other than the extent 18. As a result, the electromagnetic wave having the prescribed frequency is transferred between the waveguide 13 and the waveguide 14 through the resonator 15. On the other hand, it is suppressed that electromagnetic waves other than the prescribed frequency which become noise are transferred between the waveguide 13 and the waveguide 14 in the extents other than the prescribed extent 18. This electromagnetic wave frequency filter can be suitably constituted using a two-dimensional photonic crystal.