An up-to-date literature overview on relevant approaches for controlling circuital characteristics and radiation properties of dielectric resonator antennas (DRAs) is presented. The main advantages of DRAs are discussed in detail, while reviewing the most effective techniques for antenna feeding as well as for size reduction. Furthermore, advanced design solutions for enhancing the realized gain of individual DRAs are investigated. In this way, guidance is provided to radio frequency (RF) front-end designers in the selection of different antenna topologies useful to achieve the required antenna performance in terms of frequency response, gain, and polarization. Particular attention is put in the analysis of the progress which is being made in the application of DRA technology at millimeter-wave frequencies.

A comparative analysis of various reconfigurable and multiband antenna concepts is presented. In order to satisfy the requirements for the advanced systems used in modern wireless and radar applications, different multiband and reconfigurable antennas have been proposed and investigated in the past years. In this paper, these design concepts have been classified into three basic approaches: tunable/switchable antenna integration with radio-frequency switching devices, wideband or multiband antenna integration with tunable filters, and array architectures with the same aperture utilized for different operational modes. Examples of each design approach are discussed along with their inherent benefits and challenges.

A class of printed antipodal drop-shaped dipole antennas for wideband wireless communication systems is presented. A suitable shaping of the feeding lines and radiating arms is adopted to achieve an operating bandwidth larger than 10 GHz useful to meet the requirements of several wireless communication standards. A thin, low permittivity dielectric substrate is used to reduce the excitation of surface waves which are responsible for a degradation of the radiative characteristics. The proposed antenna structures present a reduced occupation volume which allows an easy integration in mobile terminals, as well as in radio base stations. A locally conformal FDTD numerical procedure has been adopted to analyze the radiating structures. An equivalent circuit, useful to predict the frequency-domain behavior of the scattering parameters of a two-element array formed by the proposed structures, is also presented. The numerical results concerning the antenna parameters are found to be in good agreement with the experimental measurements

A wideband -shaped microstrip patch antenna for wireless communications is presented. Zig-zag slots and perturbations of the -shaped metallic patch are employed to excite two resonant modes and achieve a wide-band frequency behavior, featuring a fractional bandwidth of about 30%, and, at the same time, to meet the occupation volume requirements of mobile wireless local-area network enabled communication devices. A locally conformal finite-difference time-domain numerical procedure has been employed to analyze the radiating structure. Numerical results concerning the antenna parameters are in good agreement with experimental measurements.Index Terms--shaped wideband patch antenna, wireless communications, WWLAN antennas, zig-zag slots.

An effective rigorous 3-D optical modeling of thin-film silicon solar cells based on finite element method (FEM) is presented. The simulation of a flat single junction thin-film silicon solar cell on thick glass (i.e., superstrate configuration) is used to validate a commercial FEM-based package, the High Frequency Structure Simulator (HFSS). The results are compared with those of the reference software, Advanced Semiconductor Analysis (ASA) program, proving that the HFSS is capable of correctly handling glass as an incident material within very timely, short, and numerically stable calculations. By using the HFSS, we simulated single junction thin-film silicon solar cells on glass substrates textured with one-dimensional (1-D) and two-dimensional (2-D) trapezoid-shaped diffraction gratings. The correctness of the computed results, with respect to an actual device, is discussed, and the impact of different polarizations on spectral response and optical losses is examined. From the simulations carried out, optimal combinations for period and height in both 1-D and 2-D grating configurations can be indicated, leading to short-circuit current percentage increase with respect to a flat cell of, respectively, 25.46% and 32.53%. With very limited computer memory usage and computational time in the order of tens of minutes for a single simulation, we promote the usage of 3-D FEM as a rigorous and efficient way to simulate thin-film silicon solar cells.

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Novel cylindrical dielectric resonator antennas (DRAs) having supershaped base contour and adopting plastic materials for the resonator are studied. The specialization of the supershaped DRAs to the generation of linearly and circularly polarized waves is discussed, analyzed and experimentally verified. The resulting antennas exhibit wide-band (WB) performance in terms of input impedance matching, radiation patterns, realized gain and polarization properties. The proposed class of antennas shows broadside radiation with broad and smooth patterns stable over frequency, efficient and stable radiation and wide matching bandwidths. These antennas can potentially find application as access points for indoor multimedia radio systems