Dual Mode Dielectric Resonator Filters without Iris

Two filter realizations using dual mode dielectric resonators in a simple tubular enclosure are described. The new configurations do not require iris to achieve the coupling among the resonators; thus eliminating expensively machined parts with tight tolerances. They also achieve lower midband insertion loss than comparable filters with iris, because conduct ion currents on the cavity ends are eliminated. Measured results on two 4-pole elliptic function experimental filters realized in the new structures agreed closely with theory.