Design of Directional Coupler with Left-handed Transmission Line

A dual-layer microstrip directional coupler based on left-handed transmission line is proposed in this paper. First, formulae for the design of dual-layer microstrip directional coupler with quasi-TEM waves have been deduced, then, directional couplers with dual-layer traditional microstrip line and left-handed transmission line are respectively designed for comparison. The effectiveness of the present formulae is verified by good agreement between the data calculated with the deduced formulae and the simulation results, which indicates that the length of 5-aperture directional coupler designed in left-handed transmission line is only 70% of that in traditional microstrip line, and that shows the directional couplers that consist of left-handed transmission line are more compact than traditional ones.