The Use of Ferrites at Microwave Frequencies describes the applications of ferrites at microwave frequencies and the apparatus involved. Topics covered range from the properties of ferrites to gyromagnetic and non-reciprocal effects, ferrite isolators, circulators, and modulators. The use of ferrites in variable frequency filter cavities is also discussed. Mathematical explanations are reduced to the strict minimum and only the results of calculations are indicated. This book consists of seven chapters and opens with a review of the theory of magnetism, touching on subjects such as the BOHR magneton, diamagnetism and paramagnetism, ferromagnetism and antiferromagnetism, ferrimagnetism, and demagnetizing. The next chapter deals with the elementary theory of gyromagnetic effects and covers the kinetic moment theorem, precession of the spin moment, gyromagnetic resonance, complex permeability, and gyromagnetic effects in the atom. The reader is then introduced to ferrites and their properties; non-reciprocal effects and their applications; and ferrite isolators, circulators, and modulators. The final chapter describes the use of ferrites in the design of cavities whose resonant frequency is controlled by a magnetic field or filters with variable characteristics. This monograph is written primarily for microwave and electronics engineers.