“Influence of the Directional coupler’s Parameters on the Characteristics of Butler Matrix 4×4”. Visnyk NTUU KPI Seriia - Radiotekhnika Radioaparatobuduvannia, no. 57 (June 30, 2014): 43–50. Accessed May 6, 2025. https://radap.kpi.ua/radiotechnique/article/view/783.