THIS PRESENTATION CONSISTS OF 1.Introduction 2.Purpose of DRA 3.Structure of DRA 4.Excitation methods 5.Radiation patterns 6.Factors effecting the Resonant frequency 7.Challenges 8.Conclusions 9.References INTRODUCTION The field of wireless communication has been under going a revolutionary growth in the last decade. 2G-cellular communication (portable mobile phones) 3G- Bluetooth, LAN The crucial component of a wireless network is the ‘Antenna’. In the last two decades the classes of antennas investigated and extensively reported are 1.Microstrip patch antenna 2.Dielectric Resonator Antenna INTRODUCTION TO DRA Since the frequency range of interest has gradually progressed upward and the frequencies in millimeter region(100-300Ghz) are employed, the conduction losses in metallic antennas increase to such a level that efficient operation of the systems is impaired. So an idea to use dielectric material as a radiator was conceived. Dielectric resonators were used as energy storage devices but if the cavity is not enclosed by metallic walls the EM fields exist beyond the geometrical boundary of the cavity. INTRODUCTION TO DRA The use of dielectric resonator as a resonant antenna was proposed by S.A LONG in early nineteen eighties. Dielectric resonator antennas offer advantages like small size, low cost and most importantly freedom from metallic loss. Therefore dielectric resonator antenna have a lot of applications in millimeter band where the conductor loss of a metallic antenna becomes severe. PURPOSE OF DRA As the frequency increases conductor losses increases and antenna efficiency will decreases. Conversly only losses present in the DRA are due to imperfections in the Dielectrics which are very small compared to conductor losses. Dielectric resonators which we are using in microwave applications are having (ɛ > 20) and Q(50-500). By choosing a dielectric material (5<€<20) properly the radiation fields can be enhanced. The dimension of a DRA is of the order of λo/√(ε). Thus by choosing high value of ε, the size of DRA can be significantly reduced. High Radiation efficiency(=95%)due to absence of conductor losses. High ɛr tolerance (1-5%) Wide frequency range: f = 0.7 -35GHz COMPARISION WITH MICROSTRIP ANTENNA In Micro strip radiation occurs due to narrow slots where as in DRA radiation occurs due to whole DRA surface. COMPARISION WITH MICROSTRIP ANTENNA In Micro strip radiation occurs due to narrow slots where as in DRA radiation due to whole DRA surface. DRA has wider impedance bandwidth than micro strip DRA avoids surface waves STRUCTURE OF DRA The DRA consists of a ground plane and over it a dielectric resonator is placed as shown in the figure. The dielectric resonator can be of various shapes like rectangular ,cylindrical , hemispherical, triangular ,spherical cap, circular ring etc STRUCTURE OF DRA Shapes of DRA Some examples of Dielectric materials Ref::1 An important parameter for DRA is its resonant frequency The Resonance frequency of a dielectric resonator depends on dimensions of resonator and dielectric constant. Ref::1 DRA size decreases as the dielectric constant increases Wavelength of the dielectric resonator is important because from this wave length the dimensions of Micro strip circuit can be designed. The dielectric resonator antenna is a resonant circuit that is able to store electromagnetic fields with a minimum loss of energy within the resonator i.e. a cavity with a high-unloaded quality factor, QU. Simple design of DRA using Disk shape dielectric The dielectric resonator antenna (DRA) consists of high dielectric constant materials, high quality factors and mounted on a grounded dielectric substrate of lower permittivity. The selected dielectric disk is operating at frequency of 2.4 GHz with dielectric constant of 34.73. The micro strip transmission line has been used as a feeding line for the resonator. The magnetic fields inside a DRA THE ELECTRIC FIELDS INSIDE A DRA FIELDS INSIDE A RECTANGULAR DRA The Hx component of magnetic field is dominant along the centre of DRA , while E-fields (Ey and Ez) circulate around the Hx component. Showing 2-D image of fields inside DRA Excitation Methods APERTURE COUPLING PROBE COUPLING MICROSTRIP LINE COUPLING Aperture coupling This method of exciting DRA is through an aperture in the ground plane upon which the DRA is placed. The various types of apertures are shown Showing aperture coupling Micro strip line COUPLING is preferred over the coaxial cable because it offers good impedance matching compared to the coaxial line. The length of the slot is chosen large enough so that sufficient coupling exists but small enough so that it does not resonate within the band of operation. Aperture coupling to rectangular DRA Aperture coupling to cylindrical DRA PROBE COUPLING This type of coupling employs a probe in order to couple a DRA. The probe consists of a centre pin that extends through the ground plane. This probe can also be soldered to a flat metal strip which is placed adjacent to DRA. This flat metal strip can also be modeled so that impedance matching is achieved. SHOWING PROBE COUPLING COUPLING THROUGH A METAL PLATE PROBE COUPLING TO RECTANGULAR DRA MICROSTRIP LINE COUPLING A DRA can be coupled with the help of micro strip line in two ways 1)Direct-coupling 2)side-coupling SHOWING DIRECT COUPLING SHOWING SIDE COUPLING THE MULTISEGMENT DRA(MSDRA) QU refers to the Internal energy dissipation where as the External quality factor QE refers to energy dissipation outside . The loaded Q,QL takes into account all causes of energy dissipation and is given by The experimental results The radiation patterns for different a/d ratios The radiation patterns for different €r values Radiation Pattern The HPBW for Hplane is 77.72° greater than measurement, which are 72°. The HPBW for Eplane is 46.61° for measurement and 45 °for simulation respectively. Ref:;1 There are a few factors affecting the Resonance frequency. 1 Adhesives for Dielectric Resonator. 2. Environment. 3. Equipment. 4. Fabrication process. Challenges In order to be suitable for GSM and PCS antenna, applications εr needs to be <30 DRAs with ε r <30 at frequencies below 3GHz are generally too large to be used for handsets REFERENCES  S.A Long ,M.W.McAllister and L.C.Shen ,“The resonant cylindrical dielectric cavity antenna ,”IEEE Transactions on Antennas & Propagation,Vol.31,pp.406-412,May 1983. Collin,R.E. ,Foundations for Microwave Engineering, New York: McGraw Hill,1966. A.Petosa, Dielectric Resonator Antenna Handbook, Norwood, MA:Artech House,2007. K.M.Luk and K.W.Leung, Dielectric Resonator Antennas, Baldock,U.K. : Research Studies,2003. WEBSITES: www.wikipedia.com www.antena-theory.com Thank you…..... Any queries…….