Broadband magic-Ts with the use of coupled-line directional couplers and left-handed transmission line sections
The problem of broadband magic-T realization with the use of coupled-line directional couplers and left-handed (LH) transmission-line sections has been comprehensively investigated. Broadband amplitude characteristics of the proposed networks are ensured with the use of coupled-line couplers, whereas the required phase characteristics have been achieved by the appropriate selection of right- and left-handed transmission line sections. To analyze the properties of the proposed networks, a model of an ideal left-handed transmission line has been utilized. The presented concept has been verified by two designs of broadband magic-Ts operating in 2.53.5 GHz and 0.82.3 GHz, respectively. The obtained results proved that the proposed magic-T networks allows one to obtain broadband amplitude and phase responses together with its compact structure.  2013 Wiley Periodicals, Inc. Int J RF and Microwave CAE 24:513521, 2014.
left-handed transmission lines magic-t networks 3-db directional couplers bandwidth improvement coupled-line sections metamaterials