Zhigang Zhang, Yong Fan, and Yonghong Zhang. “Multilayer Half-Mode Substrate Integrated Waveguide Wideband Coupler With High Selectivity”. The Applied Computational Electromagnetics Society Journal (ACES), vol. 34, no. 09, Sept. 2019, pp. 1418-21, https://journals.riverpublishers.com/index.php/ACES/article/view/8257.