Electromagnetic wave frequency filter

An electromagnetic wave frequency filter comprising:

• an input waveguide configured to receive electromagnetic waves of a plurality of frequencies inputted into a one end of said input waveguide;
• an output waveguide disposed alongside said input waveguide;
• and
• a resonator disposed between said input waveguide and said output waveguide, said resonator having a resonant frequency and resonating with an electromagnetic wave of a predetermined frequency matching the resonant frequency so as to transmit said electromagnetic wave from said input waveguide to said output waveguide, thereby allowing said electromagnetic wave to be emitted from a drop port of a one end of said output waveguide,
• wherein
• said input waveguide has an input-waveguide-side reflector for reflecting said electromagnetic wave of the resonant frequency on the opposite side of said one end of the input waveguide from the resonator,
• said output waveguide having an output-waveguide-side reflector for reflecting the electromagnetic wave of the predetermined frequency on the opposite side of said one end of the output waveguide,
• said electromagnetic wave frequency filter satisfying the following relation:
• Qinb/(1 cos θ1)<<Qv,
• Qinb/(1 cos θ1)=Qinr/(1 cos θ2),
• θ1, θ2≠2Nπ(N=0, 1, . . . ),
• where θ1 is a phase shift amount of the electromagnetic wave reflected by said input-waveguide-side reflector and returned to near said resonator, θ2 is a phase shift amount of the electromagnetic wave reflected by said output-waveguide-side reflector and returned to near said resonator, Qinb is a Q-factor between said resonator and said input waveguide, Qinr is a Q-factor between said resonator and said output waveguide, and Qv is a Q-factor between said resonator and free space.