The Wiley Encyclopedia of RF and Microwave Engineering ※ Ferrite Isolators ※ B. Bayard, B. Sauviac & D. Vincent November 12, 2004 Abstract Signal processing requires specialized functions, particularly in the microwave range, where wave propagation can easily be corrupted. The main applications of isolators as well as their characteristics are described. Some waveguide and planar microwave ferrite de- vices based on the Faraday effect, field displacement, or gyroresonance are then reviewed. For a better understanding of the functioning of such devices, microwave properties of ferrite materials are presented. Ferromagnetic resonance and the resulting nonreciprocal effects are also explained. Finally, more recent developments in the use of hard ferrites and in magnetic films technology are discussed. keywords impedance matching, isolation, insertion loss, nonreciprocal effects, ferrite, ferro- magnetic resonance, Faraday rotation, resonance absorption, field displacement, edge-guided mode. 1