RLC Resonant Circuits
Dielectric resonators - Microwave circuits

At frequencies above one gigahertz, passive microwave circuits consist of components such as transmission lines, coaxial cables, microstrips, waveguides, etc., as well as resonant cavities. These components have dimensions on the same order of magnitude as or greater than the wavelength of the electromagnetic wave. The dimensions of dielectric resonators are on the order of the wavelength in the material or a fraction of that wavelength, which explains why the dimensions decrease as the permittivity increases; this is explained in § 3