A Compact Microstrip Quadruplexer Using Slotline Stepped Impedance Stub Loaded Resonators

In this paper, a novel compact quadruplexer is imple- mented by using slotline stepped impedance stub loaded resonators (SISLRs) in ground plane. Four folded dual-mode slotline SISLRs with one input and four output coupled line structures are designed at difier- ent frequencies for the quadruplexer operation. By properly adjusting the geometrical parameters of a single dual-mode slotline SISLR, its flrst two resonant frequencies can be controlled, and thus it can be uti- lized to implement a second-order bandpass fllter when these resonant frequencies are suitably assigned. Furthermore, because the proposed quadruplexer utilizes the distributed coupling technique, a small circuit size can be obtained. As a result, the proposed quadruplexer occupies an extremely small area, i.e., 0:22‚0£0:25‚0 (0:36‚g£0:41‚g). Finally, good agreement between measurement and EM simulation verifles the design method successfully.