Dielectric band pass filter having an evanescent waveguide

A band pass filter comprising:

• a first flat resonator and a second flat resonator each having top and bottom surfaces on which metal plates are formed, a shorting surface electrically short-circuiting the metal plates formed on the top and bottom surfaces, a first open surface opposite the shorting surface, a second open surface perpendicular to the shorting surface, and a third open surface opposite the second open surface;
• an evanescent waveguide provided between the first and second flat resonators such that the evanescent waveguide is in contact with the entire second open surfaces of the first and second flat resonators;
• a first capacitive stub formed on the first open surface of the first flat resonator;
• a second capacitive stub formed on the first open surface of the second flat resonator;
• a first exciting electrode formed on the third open surface of the first flat resonator;
• and
• a second exciting electrode formed on the third open surface of the second flat resonator.

A band pass filter comprising:

• a first flat resonator and a second flat resonator each having top and bottom surfaces on which metal plates are formed, a shorting surface electrically short-circuiting the metal plates formed on the top and bottom surfaces, a first open surface opposite the shorting surface, a second open surface perpendicular to the shorting surface, and a third open surface opposite the second open surface;
• an evanescent waveguide provided between the first and second flat resonators such that the evanescent waveguide is in contact with the entire second open surfaces of the first and second flat resonators;
• a first exciting electrode formed on the third open surface of the first flat resonator;
• and
• a second exciting electrode formed on the third open surface of the second flat resonator,
• whereby a first resonation circuit is established between the first exciting electrode and the metal plates, a second resonation circuit is established between the second exciting electrode and the metal plates, and a coupling circuit is established between the first and second resonation circuits,
• the band pass filter further comprising means for providing an additional capacitance in parallel with the first resonation circuit and another additional capacitance in parallel with the second resonation circuit.