Shielded Structure of Composite Right/Left-Handed Transmission Line Using Substrate Integrated Waveguide and Floating-Conductor

A composite right/left-handed transmission line (CRLH-TL) using substrate integrated waveguide (SIW) with floating-conductor (SIW-type CRLH-TL) for microwave and millimeter wave frequencies has been proposed by the authors. This paper proposes a new configuration that is shield type of the SIW-type CRLH-TL, which can suppress the radiation from the exposed floating-conductors, and shows that even if the shielded structure is used, the SIW-type CRLH-TL supports the LH mode as well as the prototype. Proposed CRLH-TL consists of a SIW with slot apertures (part 1), a dielectric film with floating-conductors (part 2) and a SIW without lower conductor (part 3). A shielded SIW-type CRLH-TL for X-K band (with wide LH mode bandwidth of 6 GHz and transition frequency of 16 GHz) that satisfies the balance condition is designed. Dispersion diagram and S-parameters are derived numerically, and typical field distributions of RH and LH transmission and the zeroth-order resonance are shown. Measured result agrees well with theoretical result, by considering the accuracy performance and loss factors of the fabricated CRLH-TL. Proposed CRLH-TL has advantage of simple manufacturing, because the parts 1-3 are composed of simple planar periodic structure. It is expected to be one of the basic structure of CRLH-TL or components such as LH coupler above 10 GHz or millimeter wave frequency.