xxi
Preface
Tunable Materials with Applications in Antennas and Microwaves is written to meet the needs of
antenna and microwave engineers as well as of graduate students of Electrical & Computer En-
gineering and Physics Departments. e objective of the book is to describe the characteristics
of ferrites and ferroelectrics, which are the most common and widely known tunable materials,
as well as to introduce the reader to multiferroics. Several applications, especially in modern
wireless communication systems, can be found with the above materials.
Essentially, the book represents in a simple manner the solid state physics of tunable ma-
terials and explains their permittivity and permeability tensor characteristics. e tensors are
given for materials with infinite and finite dimensions.
e five chapters of the book address the following topics:
Chapter 1 is an introductory chapter that contains the basics of tunable materials and the
evolution of ferrites and ferroelectrics. e applications of the above materials in resonators,
filters, microstrips, striplines, antennas, phase shifters, capacitors, varactors, and frequency se-
lective surfaces are discussed.
Chapter 2 gives the characteristics and the constitutive parameters of ferrites and ferro-
electrics. It starts from different types of magnetic materials, magnetic moments, structure of
certain ferrites, and the MMICs. It explains the magnetization equation and gives the perme-
ability tensor in different coordinate systems. Also, it discusses the dielectric properties, the
polarizability, and the losses of ferrites. For the ferroelectric materials, the chapter represents
their properties, the permittivity tensor, their dielectric response, the hysteresis loop, the losses,
as well as the crystal structures of certain ferroelectrics.
Chapter 3 presents finite ferrites samples including their spin and magnetostatic modes.
Mathematical analysis is given in details for spin and magnetostatic waves for infinite medium,
thin slab films, and finite circular discs. is chapter contains original work, which the reader
may extend in the future.
Chapter 4 gives multiferroics. ese are very promising tunable materials with ferrite and
ferroelectric composites. We give certain properties, relations, and interesting characteristics. It
is believed that multiferroics will be materials with many applications in the near future.
Chapter 5 contains the planar transmission lines, which are the absolute media in the
antenna and microwave applications. In the chapter, we give analytic formulas for multilayer
xxii PREFACE
microstrips, transmission lines, and waveguides with isotropic as well as anisotropic dielectric
and magnetic materials.
John N. Sahalos and George A. Kyriacou
August 2019
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