Very Compact Diplexer Based on Dual-Mode Dielectric TM-Mode Resonators

A very compact in-line C-band diplexer is reported in this letter based on dual-mode dielectric TM-mode resonators in planar coupling configuration. In addition to the advantages of substantial volume-saving and easy assembly, the proposed diplexer features high-quality factor, enhanced spurious performance, high-power handling, and efficient tuning process with independent control of each passband. For verification purposes, a C-band diplexer is designed, implemented, and tested. The final assembled diplexer unit has a compact overall volume of 43 $\times 40\times15.9$ mm 3. It operates at 4.73 and 5.03 GHz with the same bandwidth of 24 MHz, an insertion loss better than 0.9 dB, and a return loss higher than 21 dB. In addition, a high-power breakdown analysis shows that the introduced diplexer can handle high levels of input power up to 5200 W.