The measurement of complex permittivity and complex tensor permeability of ferrite materials at microwave frequencies

A review is given of the techniques available for measuring the properties of ferrite materials at microwave frequencies. A detailed account is given of permeability and permittivity measurements in the 3 cm band using a cavity technique. The input impedance of an H11-mode cavity loaded with a ferrite disc or sphere is derived by a perturbation calculation. The equivalence between this impedance and the input impedance of two tuned coupled circuits is shown, and hence the ferrite permeability is derived from accepted circuit theory. The range and accuracy of the apparatus is discussed, and the results of measurements on a wide range of ferrites using this technique are presented.