Wanchen Yang, Wenjie Feng, and Wenquan Che. “Wideband Filtering Crossover Based on Ring Resonator With Sharp Rejection”. Applied Computational Electromagnetics Society Journal (ACES), vol. 32, no. 10, July 2021, pp. 924-8, https://journals.riverpublishers.com/index.php/ACES/article/view/9473.