Planar diplexer using composite right-/ left-handed transmission line under balanced condition

A novel high-performance planar diplexer is proposed. The filtering response of a balanced composite right/left-handed transmission line (CRLH-TL) is investigated first. The diplexer is then implemented based on two balanced CRLH-TLs. Simulated results and experimental verifications are provided, and simulation results are found to be consistent with measurement results. This diplexer shows advantages in terms of the low loss, high isolation, easy fabrication and integration with other circuits.