International Journal of Scientific and Research Publications, Volume 2, Issue 9, September 2012 1 ISSN 2250-3153 www.ijsrp.org A Circular Disk Dielectric Resonator Antenna Using a C- Slot, for Dual-frequency operation Nishita Sahoo * , Anil Kumar ** , Charlie Eapen ** , Ravi Jon ** * Department of Electronics and Communication Engineering, Sam Higginbottom Institute of Agriculture, Technology and Sciences. ** Department of Electronics and Communication Engineering, Sam Higginbottom Institute of Agriculture, Technology and Sciences. Abstract— The high demand for faster and more reliable services in several applications of modern communications increases the requirements for a large data transmission capacity and hence a wide operational bandwidth. In addition to that, mobile communication set some strict specifications concerning the size, the weight and the efficiency of the RF front-ends, which are responsible for the transformation of the base-band signal to a radiated electromagnetic wave and vice versa. The element of the RF front-end, mainly determines the size and the efficiency of the antenna. In this paper, dual-frequency is obtained, using cylindrical dielectric resonator antenna with a parasitic c-slot fed by a microstrip line. The structure consists of two radiating resonators that are tightly stacked together and resonate at different frequencies. The first frequency is from the DRA and the other from the c-slot. The use of dielectric resonator in feeding circuit requires accurate knowledge of the coupling between the resonator and circuit. So, in order to match the dielectric resonator to the feedline and to excite the HEM 11δ mode in the resonator, the most common method of feeding technique used is aperture-coupled arrangement. The proposed DRA is suitable to be mounted above the system circuit board of the mobile communication devices, and is very suitable for application in mobile communication systems. Index Terms— Ceramic dielectric material, dielectric Resonator Antenna (DRA), dual band, microstrip feedline. I. INTRODUCTION ince the early 1970s dielectric resonators of very high permittivity (relative dielectric constant of the order 100 − 300) were used as resonant cavities for different active and passive microwave components including filters, oscillators, amplifiers and tuners. Van Bladel was the first to examine the properties of these resonators; his work focused on the classification of the excited modes as well as on the investigation of the fields‘ distributions. This examination was made under the hypothesis that the structures are strictly energy storage devices. For cavities, however, that are not enclosed by metallic walls, electromagnetic fields can also be detected beyond the geometrical boundaries of the resonator. When the dielectric permittivity is very high, the radiation loss is negligible and the unloaded Q factor of the resonator is mainly limited by the dielectric losses. On the other hand, the decrease of the dielectric permittivity value results in an increase of the amount of energy ‘lost‘ in the form of radiation and hence in a degradation of the resonator‘s operation as a cavity. Long et al. demonstrated in 1983 that dielectric resonators made of low permittivity materials (8 ≤ εr ≤ 20) and placed in open environments exhibit small radiation Q-factors if excited in their lower-order modes. The high radiation losses of these resonators make them particularly useful as radiating elements, especially in high-frequency applications where ohmic losses are a serious problem for the conventional metallic antennas. Apart from their low dissipation loss and the subsequent high radiation efficiency, DRAs offer many other attractive features, such as good mechanical and temperature stability, compatibility with MIC‘s, low mutual coupling in array configurations and most importantly, a small size and weight due to the scaling of the DRA dimensions with the permittivity according to the relation λ 0 / √ε r, with λ0 being the free-space wavelength. Moreover, the DRAs‘ versatility in terms of their shape and feeding mechanism allows for the efficient control of the excited modes and thus of the input impedance, the bandwidth, the polarization and the radiation patterns. Different DRA modes can be excited through various feeding techniques using conventional transmission lines, while the DRA shape and permittivity can be varied in order to accommodate different design requirements. The most common dielectric resonator geometries are canonical shapes such as the parallelepiped, the cylinder and the sphere/hemisphere, but depending on the application, various noncanonical shapes may also be encountered. Concerning now the electric properties of the dielectric resonators, a large number of suppliers worldwide provide linear, non-dispersive, low-loss materials demonstrating a wide range of dielectric permittivity values. One of the most important challenges in the design of an antenna is its bandwidth response. Modern communications set the bandwidth requirements very high and the antenna technology needs to keep up with them. DRAs are inherently more wideband than other resonant antennas like for example the microstrip antennas. Hence, DRAs exhibit a higher Radiation Power Factor (RPF), or in other words, a lower Q-factor than microstrip antennas. Since, however, DRAs are resonant structures, they are, in principle, narrowband. Even for a DRA of a low dielectric permittivity ε r = 10, the bandwidth response does not exceed (10 – 15)%, which is not always enough for many commercial applications. The DRA bandwidth can be increased through the reduction of the dielectric permittivity according to S