ABSTRACT
This chapter looks at research carried out in the area of tunable surfaces. It introduces the reader to a number of different tuning techniques that were developed over the years. The chapter presents the reader to a number of popular surface-tuning techniques. Traditional electromagnetic bandgap materials were always bound to a fixed frequency response. Conducting elements normally etched on substrates maintain fixed geometric patterns, and these types of surfaces were limited in their frequency performance. Tunable surfaces mainly rely on the principle of changing the surface impedance of a periodic array through novel control methods. Substituting a ferroelectric material instead of a ferrite-based material as the substrate allows the permittivity to be tuned using a biasing electric field. In many ways, mechanical tuning can be seen as a very simple method for tuning frequency characteristics of surfaces. Varactor diodes have found many uses in Radio frequency applications, especially in tunable devices.
