Compact six-band triplexer using stub-loaded stepped impedance resonators

A novel six-band triplexer based on short- and open-ended stub-loaded stepped impedance resonators (SLSIRs) is presented. The stub added at the centre of the SIR introduces a flexible even mode close to the first odd mode, realising a dual-band response with nearby passbands and a wide stop band. Three second-order dual-band channels combined with a common T-shaped SIR feed line form a six-band triplexer with compact size, low insertion loss and high isolation. A practical six-band triplexer operating at 1.9/2.4, 3.5/4.2 and 5.2/5.8 GHz is designed and realised based on the proposed multi-band multiplexer coupling scheme.