Microstrip diplexer based on common dual-band filter

A novel microstrip diplexer with novel coupling structure is proposed in this letter. The proposed diplexer is designed with several stepped-impedance resonators. A dual-mode dual-band filter unit is used in this design to replace the conventional matching network, what is more, the dual-mode dual-band filter unit is resonance with other circuit resonator. The diplexer size can be reduced efficiently in this way. The proposed diplexer is composed by two four-pole chevbyshev filters with six stepped-impedance resonators. Based on the structure, a diplexer with the central frequency of 1.89GHz and 2.35GHz for 4G wireless communication application is fabricated and measured. Good agreements between measured results and simulated results verify the proposed structure well.