Electrical filter employing transverse electromagnetic mode coaxial

Abstract

An electrical filter comprising a cylindrical metal case having an aperture extending in a line, a plurality of 1/4 wave length transverse electromagnetic mode coaxial resonators inserted in the aperture of the metal case in an electrical series fashion, each resonator including a dielectric resonator comprising a cylindrical dielectric material, an outer conductor and an inner conductor, the open circuit ends of the adjacent dielectric resonators being capacitively coupled and the short circuit ends of the adjacent dielectric resonators being inductively coupled by means of a coupling electrode having a coupling window. Preferably, a portion of the dielectric material having a lesser influence upon the fundamental mode is made in a lower dielectric constant to improve the spurious response characteristic. In another embodiment of the invention, a rectangular parallelepiped metal case is provided, wherein two or more apertures are formed in parallel rows, and the plurality of dielectric resonators are arranged in parallel rows but in an electrical series fashion.