TM-Mode Dielectric Resonator Filter and Diplexer With Transmission Zeros Using Extracted-Zero Technique

In this paper, a TM-mode dielectric resonator (DR) filter panel is discussed, which was designed as a concept study for the implementation within UMTS base stations for Asia marked. To avoid interference with other communication bands, stronger blocking of signals in close vicinity of the lower side of the RX passband was required. To meet the stringent specification masks, the implementation of transmission zeros (TZs) is required. Within this design study, the TZs have been realized applying the extracted-zero (EZ) technique by implementing two offline resonators which are directly coupled to the first/last resonator of the filter, respectively. To the best of our knowledge, this is the first time to report the EZ technique for the application with TM-mode DR. Furthermore, the same type of ceramic rod was applied for the design of TX, RX, and EZ resonators by suitable dimensioning of their enclosure. The design is discussed and measurement performance of a filter panel prototype is presented.