A via-free microstrip left-handed transmission line

Abstract

A via-free microstrip left-handed (LH) transmission line (TL) is proposed, which enables easy and low-cost fabrication of backward wave TLs. Based on the equivalent circuit, dispersion characteristics of the TL are theoretically obtained and the effect of the virtual short capacitance on the LH bandwidth is shown. The balanced/unbalanced CRLH criterion for seamless transition from the backward and forward wave propagation is also derived. The microstrip LH TL is implemented and the backward wave support is confirmed both by full-wave FEM simulations and experiments. A 38-cell TL exhibits a backward to forward scanning leaky-wave antenna capability.