Size reduction and wide bandwidth rat-race coupler with shunt capacitors and composite Right/Left-Handed Transmission Line

This paper introduces a rat-race coupler, with size reduction and bandwidth enhancement, using shunt capacitors, high impedance lines and Composite Right/Left-Handed Transmission Lines (CRLH-TLs). The reduced method of line length is used to combine a short length high impedance line and two shunt capacitors. Also, there is combined CRLH meta-material, using nonlinear phase characteristic of CRLH-TL that consists of series capacitors and shunt inductors, so as to obtain wide bandwidth. The implemented rat-race coupler shows a novel design with compact size that is smaller by 10% and a bandwidth that is larger by 60% than that of a conventional rat-race coupler.