Coexistence-Mode Composite Right/Left-Handed Transmission Line and Its Application for Folded C-Type SIW Butler Matrix

In order to meet the widespread application of the large-scale integrated circuits in the future and reduce the size of the multibeam array antenna. The miniaturized beamforming network (BFN) is the key to solving the large size of the multibeam array antenna. In this paper, a novel transmission line technology based on the coexistence mode composite right/left-handed (Comode CRLH) folded C-type substrate integrated waveguide (FCSIW) is presented. The interdigital slot (IDS) is introduced into the traditional FCSIW transmission line to realize the dynamic control of the folded TE
10
mode and the folded TE
20
mode. By increasing the difference between the two modes of the phase constants, the miniaturized directional coupler and the miniaturized cross coupler can be realized. Finally, the Co-mode CRLH
$4 \times 4$
FCSIW butler matrix (BM) is obtained. Compared with the traditional FCSIW counterparts, the longitudinal size of the proposed BM is reduced by 30.7%.