The performance of a pair of axially magnetized ferrite coupled lines (FCLs) is studied numerically, taking into account the reflections at both input and output interfaces for the first time. It is found that the peak power transfer factor (operation frequency) of a microstrip FCL decreases (increases) when the saturation magnetization increases. It is also predicted that broad bandwidth is possible for FCLs built on strip line. The influence of a metal enclosure and other parameters of the FCL such as ferrite thickness, separation of the coupled lines, etc., are also discussed. ¿ 2001 American Geophysical Union