Diplexer using composite right-/left-handed transmission line

Any two ports of a lossless reciprocal three-port network can be matched and let another one be mismatched completely. The composite right- /left-handed transmission line (CRLH-TL) has the dual-band property because of its unique hyperbolic-linear dispersion relation. Based on the dual-band property, a novel three-port diplexer is proposed by combining two three-port networks operating at different frequencies. Theoretically, such a three-port diplexer can be designed to operate at two arbitrary frequencies. The simulation results show that the three-port diplexer can separate two different frequencies effectively, and simulation results are found to be consistent with measurement results.