《《True Inline Cross-Coupled Coaxial Cavity Filters》.pdf

2958 IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES, VOL. 57, NO. 12, DECEMBER 2009 True Inline Cross-Coupled Coaxial Cavity Filters Ying Wang, Member, IEEE, and Ming Yu, Fellow, IEEE Abstract— In this paper, a novel true inline configuration for resonating or nonresonating structures and may lead to spurious cross-coupled coaxial cavity filters is presented, which is charac- peaks at out-of-band frequencies [9]. Furthermore, for an inline terized by a simple and compact structure, improved performance, implementation, it is necessary to couple the input and output to and good tunability. Instead of using folded structures, dedicated coupling probes, or extra cavities, as required by conventional the second and the second to last resonators. Additional wirings techniques, cross coupling is realized by changing the orientation are needed in order to move connectors to the two ends of the of selected resonators. Sequential coupling between adjacent filter housing. resonators and cross coupling between nonadjacent resonators Another well-known solution for combline filters is to use a are effectively controlled by introducing small metal plates at coupling probe embedded in the housing of the filter. Fig. 1(a) different locations. A six-pole bandpass filter with two transmis- sion zeros was built and tested. The measurement and simulation demonstrates the coupling and routing schematic of an example results agree very well, demonstrating feasibility of the inline filter six-pole filter with one transmission zero. In Fig. 1(b), the configuration. It enables compact design with improved resonator cross coupling between resonator 1 and 3 is realized by a probe compared to convent