Unbalanced-/Balanced-to-Unbalanced Diplexer Based on Dual-Mode Dielectric Resonator

The design of compact unbalanced-/balanced-to- unbalanced diplexer (U2U/B2U) based on full dual-mode dielectric resonator (DR) is investigated for the first time. The relationships of the external quality factors ( Q
_e
) under the two modes are analyzed. It is found that the Q
_e
of two modes can be controlled independently, which makes the design procedure simple and efficient. Based on the analysis, both of the proposed U2U and B2U diplexer can be easily built by properly adding feeding probes for the DR without increasing the circuit size by altering the location of the feeding probes according to the distribution of the electromagnetic fields. To verify the proposed design concept, the diplexers mentioned above are simulated, implemented and measured. The isolation is achieved by the orthogonality between modes while the low insertion loss is obtained due to the high unloaded quality factor ( Q
_u
) of the dual-mode DR. The measurements are in accordance with the simulated results, showing low loss and good selectivity.