A novel structure to design a microstrip triplexer for wireless and WiMAX applications is presented. To obtain a compact microstrip layout, step impedance resonators and coupled lines are used. The introduced triplexer has a size of 0.35λg×0.26λg, where λg is calculated at 2.3 GHz. Also, the obtained insertion losses are 0.78 dB, 1.1 dB and 0.62 dB at 2.3 GHz, 3.2 GHz and 3.6 GHz, respectively. The LC model of the presented resonator is investigated to tune three resonance frequencies by calculating numerical values of inductors and capacitors. Finally, the designed triplexer is simulated and measured.
