I'm curious about this paper's subsequent investigation, it provide a effective way by employing centered vias instead of iris-type vias to improve the SIW crossover's isolation, but there's no explanation about why it can improve the isolation.
References:
Salem Hesari, S., Bornemann, J.: ‘Substrate integrated waveguide crossover
formed by orthogonal TE102 resonators’. Proc. 47th European Microwave
Conf., Nuremberg, Germany, October 2017, pp. 1–4