Laila K. Hady

Dual-Band Compact DRA With Circular and Monopole-Like Linear Polarizations as a Concept for GPS and WLAN Applications

The concept of achieving a dual-band antenna with two different radiation patterns using a single cylindrical dielectric resonator is presented. Both simulated and experimental measured results are conducted to prove the validity of the proposed concept. A broadside circularly-polarized pattern with 7% bandwidth and a vertically polarized omnidirectional pattern with 17.3% bandwidth are obtained, simultaneously. The minimum measured axial ratio is found to be 1.3 dB. The front-to-back ratio is measured to be 15 dB. A design suitable for both Global Positioning System and wireless local area network applications is proposed.

Triple Mode Use of a Single Dielectric Resonator

A single dielectric resonator is used for a triple mode operation in filtering and dual band radiation purposes. A high unloaded quality factor over 2300 at 2.43 GHz is obtained simultaneously with both broadside and omni-directional radiation patterns of 7% and 8% bandwidths around 2.47 and 3.36 GHz, respectively. Series of parametric studies are developed to tune the filters operating frequency range, to enhance its insertion loss and to obtain a sharp filtering skirt behavior. Finally, measurements of both filter insertion loss and antenna return loss, coupling coefficients and radiation patterns are illustrated for further verification.

Electromagnetic Scattering from Conducting Circular Cylinder Coated by Meta-Materials and Loaded with Helical Strips Under Oblique Incidence

The asymptotic strip boundary condition (ASBC) is applied to analyze the solution of the electromagnetic scattering from a conducting cylinder coated with a homogeneous linear material layer and loaded with conducting helical strips. Such homogeneous material layer can be implemented by a conventional dielectric material, a single negative (SNG) or double negative (DNG) meta-material layer. A study of different materials’ constitutive parameters is presented with accordance to Drude and Lorentz material modeling. The boundary condition assumes that the strips are rounded around the coated cylinder in a helical form and both the strip’s period and the spacing between the helix turns are very small and mathematically approaching the zero. Scattering due to normal and oblique incident plane waves (θi, φi) of arbitrary polarization using the series solution is also computed. A number of parametric studies were investigated to illustrate the advantages of using metamaterials compared with conventional coating materials in terms of strip’s rounding pitch angle and coating layer electrical thickness variations. It is also shown that for SNG materials, modified Bessel functions are used to accept negative arguments. Coating with metamaterials proves to achieve higher forward scattering compared with conventional materials for the same electrical coating thickness.

Dielectric Resonator Antenna in a Polarization Filtering Cavity for Dual Function Applications

A new concept of dual mode operation for oscillation and radiation characteristics using single dielectric resonator enclosed by modified rectangular cavity has been developed. High unloaded quality factor of 2700 at 2.54 GHz and omni-directional radiation patterns with radiation bandwidth of 5.13% around 3.31 GHz were achieved simultaneously. The high-Q mode is coupled to a microstrip line and the low-Q mode is coupled to a coaxial probe with capacitive plate. Reaction-type measurement of the unloaded Q factor with the help of a network analyzer is described in details. Measurements of the scattering parameters and of the radiation patterns were carried out to verify the simulation results.

Dual function of a dielectric resonator: A high-Q resonator and a low-Q radiator

A new concept of dual mode operation for oscillation and radiation characteristics using single dielectric resonator enclosed by modified rectangular cavity has been developed in this paper. High unloaded quality factor of 2700 at 2.54 GHz and omni-directional radiation patterns with radiation bandwidth of 5.13% around 3.31 GHz were achieved simultaneously. The high-Q mode is coupled to a microstrip line and the low-Q mode is coupled to a coaxial probe with capacitive plate. Measurements of the scattering parameters and of the radiating patterns were carried out to verify the simulation results.

Five-way power divider based on dielectric resonator whispering-gallery modes

The use of whispering-gallery mode dielectric resonator (WGMDR) in the design of X-band 5-way power divider is presented. A combination of probe type of excitation integrated with microstrip technology are used to excite an H-polarized resonating mode around 10.85 GHz. For uniform power distribution, a cylindrical dielectric resonator is enclosed within a shielded cavity. Both input matching and equal power distribution are experimentally maintained within 200 MHz frequency band around the resonance. Measured scattering parameters magnitude and phase of the proposed 6-port structure are carried out to verify the expected simulation results.

Power Dividers Based on Dielectric Resonator Whispering-Gallery Modes Fed by Probe or Slot Type of Coupling

The use of whispering-gallery mode dielectric resonator (WGMDR) in the design of X -band five-way power divider is presented. Different excitation techniques are proposed to excite the higher order whispering-gallery H-polarized resonating mode such as probe excitation and C-slot type of coupling integrated with microstrip feeding technology. The cylindrical dielectric resonator is enclosed within a cylindrical shielding cavity to prevent radiation losses. Due to the natural behavior of the performed resonating mode, an out of phase equal power distribution can be observed. To obtain an in-phase power distribution, the adjacent C-slots are rotated with respect to each other for phase compensation. Both input matching and equal power distribution are experimentally maintained within several hundreds of megahertz frequency band around the resonance. Measured scattering parameters magnitude and phase of the proposed six-port structure are carried out to verify the expected simulation results for the different proposed excitation techniques.

Dielectric resonator with triple modes for triple functions

A triple mode operation for filtering and dual band radiation purposes is presented using a single dielectric resonator. A promising filter insertion loss value of −1.2 dB is obtained at 2.43 GHz simultaneously with both broadside and omni-directional radiation patterns of 6.8% and 7.12% bandwidths around 2.49 and 3.37 GHz, respectively. A tuning method for the filtering mode operating frequency is introduced to make it coincide with the broadside antenna frequency. Finally, measurement characteristics of the three functions are performed and compared with computed ones.

Dielectric resonator antenna utilization as a direction finder

The new concept of having a dual mode operation using a single dielectric resonator has been designed and simulated for both radiation and direction-finding purposes. The main concept was based on the rat-race ring hybrid circuit design. Promising results were obtained for the simulated design geometry and future experimental work will be done for verification. The current development in the use of dielectric resonator antenna in multi-functional realizations will add a new attractiveness to the use of dielectric resonator antennas compared with their conventional counterparts. The proposed configuration can also serve in the design of reconfigurable antennas with different radiation patterns with simple design modifications and adding the active switch circuit part.

Dual band dielectric resonator antenna for GPS and WLAN applications

This paper discusses the concept of having a dual band antenna for GPS and wireless communication system applications with the use of a single cylindrical dielectric resonator. A circularly polarized HEM11delta mode is excited at 1.575 GHz to cover the GPS L1 frequency band with a bandwidth of 9% while an omni-directional radiation pattern is obtained by coupling the resonator to the TM01delta radiating mode for WLAN system applications around 2.45 GHz and with 7.4% radiation bandwidth. The return loss and radiation patterns are illustrated for concept verification.