Theoretical Study on Creation Mechanism of Self-resonance Occurred in Unit Cells of Multilayer CRLH Transmission Lines

Abstract

A multi-layer composite right/left-handed (M-CRLH) transmission line (TL) was firstly proposed in 2004 as a new architecture to realize super-compact left-handed metamaterials, and the latest LTCC-based M-CRLH TL, with dimensions of 1.5mm×1.5mm×0.95mm, has a wide, flat, and low-insertion-loss passband with a fractional bandwidth of more than 130%. However, it still suffers from a deep transmission zero (TZ) yielded in a right-handed frequency region. This paper develops a new equivalent circuit model based on electromagnetic field simulations and explains creation mechanism of the TZ successfully by considering an inner-coupling in the unit-cell. Based on this argument, an ultra wideband TZ-free M-CRLH is designed and demonstrated.