DRA

1. Objective Cylindrical dielectric resonator antennas was The firs candidate for the purpose.

2. Introduction to Antennas An Antenna is a device that is used to transmit and/or receive electromagnetic waves. Oscillating current and charge create oscillating magnetic field & oscillating electric field resp. which radiates EM waves at transmitter side and reverse thing would be happen at receiver side.

3. ISM BAND The ISM (industrial, scientific and medical) radio bands were originally reserved internationally for the use of RF energy for industrial, scientific and medical purposes other than communications. Examples of applications in these bands include radio-frequency process heating, microwave ovens, and medical diathermy machines. The powerful emissions of these devices can create electromagnetic interference and disrupt radio communication using the same frequency, so these devices were limited to certain bands of frequencies.

4. A dielectric material is an electrical  insulator that can be polarized by an applied electric field. Dielectric Polarization arise in an Electric Field Dielectric Material positive charges displaced toward the field & negative charges shift in the opposite direction due to which an internal electric field creates that reduces the overall field within the dielectric itself.

5. Dielectric Resonator Generally, DRA operates at microwave & millimeter wave bands.At millimeter wave frequencies, metal surfaces become lossy reflectors, so dielectric resonators are used at these frequencies. At resonant frequencies, the microwaves form  standing waves in the resonator, oscillating with very large amplitudes. When a dielectric resonator is not entirely enclosed by a conductive boundary, it can radiate, and so it becomes an antenna. . Similar to cavity resonators , except that the radio waves are reflected by the large change in permittivity rather than by the conductivity of metal.

6. Types of Dilectric Resonator Antenna Types of DRA Cylindrical Hemispherical Rectangular DRA

7. Wireless Communication Applicability Design Flexibility Fr and Q are dependent o On R/H Why Cylindrical DRA? Provide more flexiblity in terms of BW

8. Thus the rectangular DRA can be made very compact with a small footprint area, or very low profile, or its bandwidth can be adjusted for a given material permittivity. This flexibility is further enhanced by the fact that a wide variety of feed mechanisms can be used to excite the rectangular DRA, making it amenable integration with current technology.

9. Advantages of DRA DRA size is proportional to , hence size will reduce. Compared with the microstrip antenna, DRA has a much wider impedance bandwidth. DRAs have a high dielectric strength and hence higher power handling capacity No inherent conductor loss for a DRA. High radiation efficiency is thus possible in case of DR antennas

10. DRA Design

11. We have used Aperture slot fed by microstrip line: Aperture slot: advantage of having the feed network located below the ground plane, Isolate the radiating aperture from any unwanted coupling or spurious radiation from the feed. Microstrip line: offer a degree of impedance matching not available with coaxial lines or waveguides

13. => Infinite number of resonant modes. • The excited modes for rectangular DRA can be classified into three distinct types: TE, TM, and HEM(hybrid). • On the equatorial plane, the TE and TM modes are axisymmetric, while HEM modes are azimuthally (φ) dependent. • TE0np+δ • ΤΜ0np+δ and • HEMmnp+δ The first index (m), denotes the number of full-period EM field variations along the azimuth direction with m = 1, 2, 3, … . For TE (transverse electric, no Ez component, i.e. Ez=0) and TM (transverse magnetic, no Hz component, i.e. Hz=0) modes m = 0, since the fields are axisymmetric – no variation takes place and the field remains constant in the azimuth direction. For HEM modes ‘m’ is a value always greater than zero.

14. TE0np+δ ΤΜ0np+δ and HEMmnp+δ The second index (n) implies the variation of the half wave field along the radial direction (based on the fact that the field is measured between circle’s center and the periphery), with n = 1, 2, 3, … . Finally, the index ‘p+δ’ implies the half-wave variations along the z-axis of the cylindrical resonator, with p = 0, 1, 2, 3, … . The presence of the ‘δ’ factor indicates that the half-wave field is greater than the length (thickness, if cylinder’s axis is oriented along z-axis) of the resonator itself, with 0< δ < 1. This is because of the imperfect boundary conditions at the resonator’s dielectric-air interface. This results in some EM field escape; the standing wave interior to the resonator along z-axis is less than a half-wave and decays away from the faces. The actual value of ‘δ’ depends on several physical parameters including the value of er.

15. When the DRA is mounted on a ground plane, the even modes in the z-direction (i.e., n = 2N, N = 1, 2, 3...) will be short-circuited, and only the odd modes (n = 2N+1) can exist. The modes with (m > 1, n = 1) are not of interest, since they produce a broadside null in the radiation pattern.

16. DRAs were simulated to resonate in the modes, henceforth referred to as TEδ11 , TEδ13 and TEδ15 modes, henceforth referred to as (m,n) =(1,1) , (1,3) and (1,5), respectively, all at approximately 10.75 GHz. • Two degrees of freedom, there is no unique set of dimensions for a given resonant frequency and dielectric constant. • εr = 10 to maintain a reasonable impedance bandwidth. (Higher dielectric constants would result in more compact designs but with narrower bandwidth.)

18. HFSS (Simulation Software) HFSS stands for High Frequency Structure Simulator. It is used for simulating 3-D full wave electromagnetic fields such as it is one of several commercial tools used for antenna design, and the design of complex RF electronic circuit elements including filters, transmission lines.

19. HFSS (Simulation) TE11 TE 13 TE15

20. Summary and Conclusion: This model predicts that a rectangular DRA operating in a higher order mode will radiate a more directive pattern. Simulations showed that a rectangular DRA excited in the TEδ15 mode has a directivity of nearly 12 dB, compared to 6.4 dB of the lowest order mode. Measured patterns from fabricated prototypes showed that gains of up to 10.2 dBi were achieved for a DRA operating in the (m=1,n=5). (advantage of this approach for enhancing gain compared to some of the other cited techniques lies in the smaller area requirements). Simulations show that exciting the (1,7) mode of a rectangular DRA increases the directivity to 13.7 dBi. However, such a DRA designed at 11 GHz would require a height of 90 mm, which would probably find very limited practical applications.

21. Thank you!