@article{CTT100809437,
  author = {T. Tomura and D. Kim and M. Wakasa and Y. Sunaguchi and J. Hirokawa and K. Nishimori},
  title = {A 20-GHz-band 64×64 hollow waveguide two-dimensional Butler matrix},
  journal = {IEEE Access},
  year = 2019,
}

@article{CTT100800844,
  author = {Masahiro Wakasa and Dong-Hun Kim and Takashi Tomura and Jiro Hirokawa},
  title = {Wideband design of a short-slot 2-plane coupler by the mode matching/FEM hybrid analysis considering the structural symmetry},
  journal = {IEICE TRANSACTIONS on Communications},
  year = 2019,
}