Compact dual-band rat-race hybrid utilizing composite right/left-handed transmission lines

This paper proposes a compact dual-band rat-race hybrid composed of composite right/left-handed transmission lines (CRLH-TLs). Using CRLH-TLs with phase delays of -270 and -90 degrees at low frequency (f₁), and -90 and 90 degrees at high frequency (f₂), respectively, relative bandwidths of about 20 % can be obtained at two operating frequencies of 1.0 GHz and 1.8 GHz. Furthermore, size reduction of about 80 % can be achieved in comparison with the previous CRLH-TLs rat-race hybrid. The validity of this design procedure has been demonstrated by em-simulations and experiments.