A Novel Harmonic Attenuator Quad-Channel Microstrip Diplexer for Multi-Service Communication Systems

This work presents a novel microstrip quad-channel diplexer using two stub-loaded dual-mode resonators. The proposed diplexer operates at 2.14 GHz for WCDMA, 2.36 GHz for WLAN, 3.47 and 3.7 GHz for IEEE 802.16 WiMAX applications. Moreover, its close channels make it appropriate for Frequency Division Duplexing (FDD) schemes. The insertion losses at all passbands and isolation are improved. The proposed diplexer can suppress the harmonics so that 4th harmonic is attenuated, whereas, the previous multi-channel diplexers cannot suppress the harmonics to this level. The harmonics are attenuated without size increment so that the overall circuit size is 0.046 λg
²
. The presented quad-channel microstrip diplexer is fabricated, where the results show an agreement between the simulation and measurement.