Linearly and circularly polarized conformal strip-fed dielectric resonator antennas (DRAs) are studied in this article. In the latter case, a parasitic patch is used to excite a nearly degenerate mode. The hemispherical DRA, excited in its fundamental broadside TE111 mode, is used for the demonstration. In the analysis, the mode-matching method is used to obtain the Green's functions, whereas the method of moments is used to solve for the unknown strip currents. In order to solve the singularity problem of the Green's functions, a recurrence technique is used to evaluate the impedance integrals. This greatly increases the numerical efficiency. Measurements were carried out to verify the calculations, with good results.


Keywords:

circularly polarized antenna;
dielectric antennas;
mode-matching methods;
moment methods;
parasitic antennas;
resonance

Dielectric Resonator Antennas

In recent years, the dielectric resonator antenna (DRA) has emerged as a new and viable alternative to conventional low-gain elements such as dipoles, monopoles, and microstrip patches. This practical resource presents complete, up-to-date details on DRAs in a single volume. The book provides you with clear guidance on the mode of operation and radiation behavior of DRAs, the main methods of excitation, and the major advances in DRA technology. This hands-on reference equips you with simple equations and graphs that help you rapidly design DRAs of spherical, cylindrical, and rectangular shapes, without having to resort to complex analytical or numerical calculations. You find guidelines for designing feeds required to excite the DRAs, such as probes, apertures, and microstrip lines. In addition, the book offers you various techniques for enhancing the bandwidth performance of DRAs for wideband applications. You learn how to design low profile DRAs and DRAs with circular polarization. Several approaches for designing linear and planar DRAs arrays are also considered. Moreover, this comprehensive book provides advice on the fabrication of DRAs and measurement methods used to characterize their performance. Numerous design examples are included to give you a sense of the versatility that DRAs afford.

Dielectric resonator antenna handbook

A rectangular dielectric resonator antenna (DRA) was studied theoretically and experimentally. The rectangular DRA is excited by a strip, which is compatible with a coaxial probe. Both linearly polarized (LP) and circularly polarized (CP) fields of the antenna are considered. In previous studies of the LP rectangular DRA, only the fundamental TE/sub 111/ mode has received much attention. In this paper, it is found that the fundamental TE/sub 111/ mode, together with the higher-order TE/sub 113/ mode, can be used to design a wide-band LP DRA. The bandwidth of the dual-mode DRA can be over 40% for a conventional rectangular DRA with a simple feed. For the CP mode, a parasitic patch is attached on a side wall of the DRA to excite a degenerate mode. In both the LP and CP cases, the finite-difference time-domain (FDTD) method is used to analyze the problems. The results agree reasonably with measurements.

Strip-fed rectangular dielectric resonator antennas with/without a parasitic patch

The rectangular dielectric resonator antenna (DRA) centrally fed by a probe is investigated. Its operating mode is analogous to the TM011 mode of a cylindrical DRA. The DRA radiates like an electric monopole, generating omnidirectional linearly polarized (LP) fields. Based on this LP design, a novel omnidirectional circularly polarized (CP) DRA is studied for the first time. Slots are introduced to the sidewalls of the DRA, exciting a degenerate mode for the generation of CP fields. To demonstrate the idea, an omnidirectional CP DRA was designed for WLAN (2.4-2.48 GHz) applications. The reflection coefficient, axial ratio (AR), radiation pattern, and antenna gain are studied, and reasonable agreement between the measured and simulated results is observed.

Omnidirectional Linearly and Circularly Polarized Rectangular Dielectric Resonator Antennas

A wideband omnidirectional circularly polarized (CP) rectangular dielectric resonator antenna (DRA) is investigated in this communication. An inclined slot, loaded by a parasitic conducting strip, is fabricated on each sidewall of the DRA. The parasitic strips can excite a CP mode, which combines with the CP DRA mode to provide a wideband axial-ratio (AR) bandwidth of more than 25%. To fully utilize the increased AR bandwidth, the impedance bandwidth is also broadened by introducing a hollow cylinder at the center of the DRA. The hollow region is also used to accommodate a coaxial probe that excites the antenna. The reflection coefficient, AR, radiation pattern, antenna gain, and efficiency of the antenna are studied, and reasonable agreement between the measured and simulated results is observed. A parametric study was also carried out to characterize the proposed wideband CP omnidirectional antenna.

Wideband Omnidirectional Circularly Polarized Dielectric Resonator Antenna With Parasitic Strips

A novel coupling scheme to a rectangular dielectric resonator antenna is proposed and investigated. In particular, coupling to the resonator is achieved through a narrow slot at the end of a coplanar waveguide (CPW). The objectives of this design are to maximize the coupling, match the dielectric resonator to the CPW feed line, achieve resonance at the desired frequency, obtain linear polarization with low cross polarization components, and minimize back radiation without using a back conductor. An approximate and quick design approach is given followed by more accurate design and analysis using commercial software. The antenna was fabricated and tested. Measurements match well with simulation results.

Coplanar-waveguide-fed slot-coupled rectangular dielectric resonator antenna

A novel coupling scheme to rectangular dielectric resonator antenna is proposed and investigated. In particular, coupling to the resonator is achieved through narrow slot at the end of a coplanar waveguide (CPW). The objectives of this design are to maximize the coupling, match the dielectric resonator to the CPW feed line, achieve resonance at the desired frequency, obtain linear polarization with low-cross polarization components, and minimize back radiation without using back conductor. An approximate and quick design approach is given followed by more accurate design and analysis using commercial software. The antenna was fabricated and tested. Measurements match well with simulation results. Index Terms—Coplanar waveguide (CPW), dielectric res- onators, measurement, radiation.

Coplanar-Waveguide-Fed Slot-Coupled Rectangular

The solutions to electromagnetic compatibility problems are given by combining vector finite element method (VFEM) with neural network (NN). Two methods for this combination are presented. Solution results compare well with VFEM and analytical solutions. The first method (Method 1) eliminates the need to store the memory exhaustive global matrix of VFEM. This is possible with NN since back propagation needs the estimated vector in order to compare with the right side vector. The second method (Method 2) stores the VFEM global matrix in a compact form using the sparsity and symmetry of the global matrix and then uses the stored matrix elements as the neuron's weights for the NN architecture. Further, preconditioning techniques are used to accelerate the convergence of the training algorithm. To demonstrate the applicability and usefulness of the methods, various structures are solved including crosstalk on printed circuit board, radar cross section of lossy and lossless cylinders with apertures and penetrated fields inside these cylinders.

Solutions to electromagnetic compatibility problems using artificial neural networks representation of vector finite element method

This paper addresses the problem of radar scattering from structures involving conductive regions, lossy dielectric and/or lossy magnetic materials. An example of these structures is cylinders with apertures coated by lossy materials in order to control the radar scattering from these targets. The solution for the scattered fields is based on the transverse field components rather than the longitudinal components. To this end, an absorbing boundary condition (ABC) for the transverse field components is derived. The efficiency of this ABC is analyzed and implementation details are given. The functional required to implement this ABC is verified. A computer program has been written and numerical examples are presented to show that this method is valid.

M. S. Al Salameh

Papers

Coplanar-waveguide-fed slot-coupled rectangular dielectric resonator antenna

Coplanar-Waveguide-Fed Slot-Coupled Rectangular

Solutions to electromagnetic compatibility problems using artificial neural networks representation of vector finite element method

Radar cross-section solution of coated cylinders with apertures by vector finite elements

Waves and Fields of Wireless Communications and Electricity