Compact SIW 3×3 butler matrix for 5G mobile devices

This paper presents a compact SIW (substrate integrated waveguide) 3×3 Butler matrix (BM) for 5G mobile applications. The detailed structuring procedures, parameter determinations of each involved component are provided. To validate the 3×3 BM, a slot array is designed. The cascading simulations and prototype measurements are also carried out. The overall performance and dimension show that it can be used for 5G mobile devices. The measured S-parameters agree well with the simulated ones. The measured gains are in the range of 8.1 dBi ~ 11.1 dBi, 7.1 dBi ~ 9.8 dBi and 8.9 dBi ~ 11 dBi for port 1~3 excitations.