Dielectric resonator antennas offer the following attractive features: • The dimension of a DRA is the order of \frac{\lambda_0} {\sqrt{\varepsilon_r}}, where \lambda_0 is the free-space wavelength and \varepsilon_r is the
dielectric constant of the resonator material. Thus, by choosing a high value of \varepsilon_r (\varepsilon_r\approx10-100), the size of the DRA can be significantly reduced. • There is no inherent conductor loss in dielectric resonators. This leads to high radiation efficiency of the antenna. This feature is especially attractive for millimeter (mm)-wave antennas, where the loss in metal fabricated antennas can be high. • DRAs offer simple coupling schemes to nearly all transmission lines used at microwave and mm-wave frequencies. This makes them suitable for integration into different planar technologies. The coupling between a DRA and the planar transmission line can be easily controlled by varying the position of the DRA with respect to the line. The performance of DRA can therefore be easily optimized experimentally. • The operating bandwidth of a DRA can be varied over a wide range by suitably choosing resonator parameters. For example, the bandwidth of the lower order modes of a DRA can be easily varied from a fraction of a percent to about 20% or more by the suitable choice of the dielectric constant of the material and/or by strategic shaping of the DRA element. • Use of multiple modes radiating identically has also been successfully addressed. One such example is hybrid combination of dielectric ring-resonator and electric monopole which was initially explored by Lapierre. Multiple identical monopole-type modes in an annular shaped dielectric ring-resonator were theoretically analyzed by
Guha to show their unique combinations with that due to a traditional electric monopole resulting in UWB antennas. • Each mode of a DRA has a unique internal and associated external field distribution. Therefore, different radiation characteristics can be obtained by exciting different modes of a DRA. • Differently radiating modes have also been employed to generate identical radiation patterns using composite geometries, with a special feature of wider bandwidth. ==See also==