Millimeter-Wave Multibeam Antenna Based on Folded C-Type SIW

A millimeter-wave (mm-wave) multibeam array antenna based on folded C-type substrate integrated waveguide (FCSIW) is presented for the first time. The design steps for its two main elements are described, namely an FCSIW Butler matrix (BM) and an FCSIW single-branch slot array antenna. Both of them exhibit a significant miniaturization in comparison with their substrate integrated waveguide (SIW) counterparts, leading to 40% and 33.2% reduction in occupied surface for the BM and the whole multibeam array antenna while maintaining similar performances, respectively. In addition, an optimized transition connection structure from ground coplanar waveguide (GCPW) to FCSIW is designed to facilitate the measurement of the multibeam array antenna. Finally, the FCSIW multibeam array antenna is optimized, manufactured, and measured, which can help verify the feasibility of FCSIW for the miniaturized multibeam array antenna.