TM dual mode dielectric resonator and filter utilizing a hole to equalize the resonators resonance frequencies

A high-frequency band-pass filter apparatus comprising:

• first and second cross-shaped TM dual mode dielectric resonator, each said first and second TM dual mode resonators provided in an electrically conductive case, each said TM dual mode dielectric resonator comprising first and second perpendicular dielectric resonators which are integral with each other, an operation mode of said first dielectric resonator being coupled with an operation mode of said second dielectric resonator through a mode coupling structure in each said TM dual mode dielectric resonator;
• first and second coupling loops provided in said case so that said first coupling loop is magnetically coupled to said first dielectric resonator of said first TM dual mode dielectric resonator and said second coupling loop is magnetically coupled to said first dielectric resonator of said second TM dual mode dielectric resonator;
• a partition plate of a metal material having a plurality of slits formed therein so as to be parallel to said first dielectric resonators of said first and second TM dual mode dielectric resonators, said slits being provided for magnetically coupling said second dielectric resonator of said first TM dual mode dielectric resonator with said second dielectric resonator of said second TM dual mode dielectric resonator;
• and
• each said TM dual mode dielectric resonator having a substantially empty hole for adjusting a resonance frequency of one of said first and second dielectric resonators, at an end of said one of said first and second dielectric resonators,
• wherein each said hole has a size which is predetermined in response to said magnetic coupling between said first and second coupling loops and the corresponding resonators, such that resonance frequencies of said respective first and second dielectric resonators of each of said first and second TM dual mode dielectric resonators are equal to each other.