In this paper a detailed analysis of asandwich coupled slotline with axially or transverselymagnetised ferrite layer has been carried out by usingFEM with edge elements. Comparison of dispersioncharacteristics and phase shift shows that the variablereciprocal phase shift is larger with axial bias fieldthan with transverse field, and that non-reciprocalphase shift per unit length (with transverse field) in-creases with frequency whereas reciprocal phase shiftper unit length (with axial field) decreases with fre-quency. Also conductor-backed coplanar structuresmaybe more suitable than suspended structures.