Novel microwave diplexer system based on planar waveguide and metamaterial technologies

A novel frequency diplexer was proposed in this paper, based on the integration of a SIW- CSRR bandpass filter and SIW highpass filter. SIW has the highpass characteristic as RW; CSRR is the image of SRR and takes some metamaterial features. A SIW-CSRR bandpass filter is firstly designed, and then a simple SIW highpass filter. The combination of these two filters thus leads to a simple and compact frequency diplexer. The simulated and experimental results both indicate good performances of the diplexer, especially high isolation between the transmitting and receiving paths.