Normal-mode analysis of ferrite-coupled lines using microstrips or slotlines

A normal-mode analysis of a pair of axially-magnetized ferrite-coupled lines (FCL) is presented for the first time. This normal-mode method, as opposed to the coupled-mode method, will permit optimization of propagation characteristics and impedance-matching. Also, the finite element solution of the normal modes can be used to obtain the field distribution to assist suitable placement of ferrite for device applications. Potential applications include a novel 4-port distributed microstrip circulator which may have advantages over junction devices at millimetric wavelengths. Optimum normal-mode conditions for the use of the FCL as a component in the distributed circulator are derived, and the design procedure for microstrip FCL is presented for the first time