Left-Handed Transmission Line of Low Pass and Its Applications

Abstract

We introduce a novel left-handed (LH) transmission line (TL), which is based on a structure of identical symmetrical lattice type. While all the LH-TLs reported previously are of high pass, the present LH-TL has a wide left-handed low-pass band. Compared with a conventional right-handed transmission line, this LH-TL has a phase shift difference of 180° independent of the frequency. We also analyze the effect of a non-ideal component in a practical case, i.e., when the inductance of the shorted line in the lattice section cannot be neglected. The dispersion relations between the practical case and the ideal case are given and compared. It is shown that the introduction of the inductance of the shorted line will not change the left-handedness and low-pass property of the LH-TL, but make the phase response vary slightly. In the application example of broadband 180° hybrid ring, the constant-phase-shift property of the proposed LH-TL is utilized. The broadband hybrid ring is shown to have a very high isolation and about 42% bandwidth ratio.