${\rm TE}_{01\delta}$-Mode Dielectric-Resonator Filters With Controllable Transmission Zeros

A method to design TE
_01δ
-mode dielectric-resonator (DR) filters with transmission zeros is proposed. The feeding probes, extended along ring DRs, are used to excite the TE
_01δ
mode and introduce transmission zeros. By rotating the angle of the feeding position, transmission zeros can be shifted to the lower or the upper stopband. Thus, TE
_01δ
-mode DR filters with quasi-elliptic responses are realized with only iris coupling components. Based on this method, second- and fourth-order filters with different responses are designed and fabricated. Measured results confirm the predicted performance.