A comprehensive review concerning the geometry, the manufacturing technologies, the materials, and the numerical techniques, adopted for the analysis and design of wideband and ultrawideband (UWB) antennas for wireless applications, is presented. Planar, printed, dielectric, and wearable antennas, achievable on laminate (rigid and flexible), and textile dielectric substrates are taken into account. The performances of small, low-profile, and dielectric resonator antennas are illustrated paying particular attention to the application areas concerning portable devices (mobile phones, tablets, glasses, laptops, wearable computers, etc.) and radio base stations. This information provides a guidance to the selection of the different antenna geometries in terms of bandwidth, gain, field polarization, time-domain response, dimensions, and materials useful for their realization and integration in modern communication systems.

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 novel class of special functions for electromagnetics is presented. Formed by the incomplete Hankel and modified Bessel functions, this class allows solving electromagnetics problems concerning truncated cylindrical structures. The differential and recurrence equations of these functions feature additional terms with respect to the classical theory of the Hankel and Bessel functions. The general properties, the most important analytical characteristics, and the large argument asymptotic approximations of the incomplete functions are derived using the steepest descent path (SDP) technique, showing that each special function splits into two terms. The first one has a discontinuous character and is linked to the saddle-point(s) contribution(s), while the second one, arising from the integral end-point contribution(s), compensates exactly the said discontinuity. In the solution of electromagnetic problems, the first term describes the geometrical optics (GO) field, the diffracted field being described by the second one. The general theory is employed to find the closed form analytical solution of the field radiated from a uniform line current source. Using the properties of the incomplete Hankel functions, it is demonstrated that this source excites cylindrical fields having optical character. Finally, the shape of the spatial regions where the GO solution cannot be applied is determined and discussed in details

The dyadic Green's function, transformed in the Fourier domain, is evaluated in the general case of a planar integrated structure fed by a distribution of tridimensional electrical sources arbitrarily located in the dielectric substrate. The analysis is carried out on the basis of the Maxwell's equations written for the time variation e)*' and transformed in the Fourier domain. The elements of the spectral dyadic Green's function are evaluated via the transmission-line analogy by making use of very general equivalent circuits of the planar structure determined for the case of transverse electric (TE) and transverse magnetic (TM) waves according to a general tridimensional source excitation. General properties among the elements of the Green's function are obtained, due to the electrical and geometrical symmetry of the structure, and the different roles played by the independent terms of the matrix are discussed. An expression for the power produced by the sources, evaluated through its spectral power density, is derived, and the formal representations in the Fourier domain of the input impedance for vertical and transverse sources are presented.

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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.

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

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