An important consideration in the construction and performance of
Cylindrical Dielectric Resonator Antennas (CDRAs) is the type of feed mechanism. The
Dielectric Resonator Antennas (DRAs) are very attractive candidates for a range of
applications due to their many advantageous features, such as high radiation efficiency, low
loss, flexible shape (rectangular, cylindrical, hemispherical, etc.) reduced size, low-cost
and low weight. They are simple to integrate into the existing fabrication technology
and have a flexible design process with numerous design parameters, such as shape,
size, aspect ratios and permittivity. When operating in a single mode, the bandwidth
of CDRA is typically below 10%. Extensive research has been devoted to widening
the bandwidth of DRAs by using co-polar parasitic DRAs (Long et al., 1983), stacked DRAs (Kishk et
al., 1989), deforming the geometry (Kishk et
al., 2002) and loaded DRAs (Kishk et al., 2001). So far, the two most popular excitation schemes are
vertical metallic probes and coupling slots in ground plane of microstrip line (Drosses et al., 1999). Slot coupled DRAs may find advantages over probe-fed DRAs in terms
of bandwidth and in reduction of ohmic losses. To achieve a proper match with
the source, the slot must be properly adjusted. The improvement in bandwidth is
due to the flexibility offered by the slot length and coupling slot size. In the
cylindrical DRA, the resonant frequencies of the dominant mode and the similarly
radiating higher order mode can be modified by adjusting the height of the
Dielectric Resonator (DR). This is done by suitably choosing the radius to height ratio
(r/h) of the CDRA. This provides a wide bandwidth over a desired frequency range (Chair et al., 2005).
In this paper, the study is made to gain a bandwidth enhancement technique
of CDRA by increasing the height of DR. The antenna is composed of DR and a
coupling slot, which acts as an effective radiator and feeding structure for the DR. Both
DR and slot are resonant structures, which yield multiple resonant frequencies with
low cross-polarization levels. |
