Massimiliano Simeoni

A Low-Profile Printed Drop-Shaped Dipole Antenna for Wide-Band Wireless Applications

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.

Plastic-Based Supershaped Dielectric Resonator Antennas for Wide-Band Applications

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.

Interleaved Array Antennas for FMCW Radar Applications

An effective and robust strategy for concurrently designing the transmit and receive antennas of a frequency-modulated, continuos-wave radar is discussed. The aperture architecture is based on the use of non-periodic, interleaved sub-arrays. Deterministic element placement is employed for ensuring design efficiency. The procedure yields controllable sub-array radiation patterns and two-way side-lobe levels below - 30 dB, that are also stable over a wide frequency range.

Implementation of polarization agility in planar phased-array antennas by means of interleaved subarrays

A method for ensuring polarization agility in conjunction with beam steering in planar array antennas is proposed. It relies on interleaving two subarrays with orthogonal, linear polarizations that, together, can generate arbitrary polarization states: adjustable linear, elliptical, and left- or right-handed circular. The complexity of the resulting system is comparable with that of standard, fully populated array antennas consisting of identical, linearly polarized elements. By dynamically controlling the amplitude and the phase of the signals fed to the subarrays, a stable polarization state can be maintained during beam steering. The concept is validated by numerically investigating an architecture obtained by interleaving nonuniform subarrays designed by means of a deterministic placement strategy. The effects of the mutual coupling between the different radiating elements are modeled and discussed.

Experimental investigation of the mutual coupling reduction by means of cavity enclosure of patch antennas

The mutual couplings between patch antennas printed on a common dielectric board is evaluated experimentally. Two variants of this type of radiators are taken into account: with and without a cavity enclosure of the patches. Experiments are conducted on patch antennas manufactured in a standard printed circuit board (PCB) technology. The presence of cavities, fabricated by means of equally-spaced, metal-plated through-holes surrounding the antennas, reduces the amount of energy flowing from one radiator to another.

Interleaving sparse arrays: a new way to polarization-agile array antennas?

A new strategy to obtaining polarization-agile array antennas was discussed. It makes use of the interleaving of sparse (complementary) sub-arrays characterized by mutually orthogonal, linear polarizations. The validity of this approach was demonstrated by examining two examples of arrays designed for obtaining adjustable linearly-polarized waves. The advocated technique allows a significant reduction of the control circuitrys complexity and the use of simple radiators, while guaranteeing the possibility to obtain complex and reconfigurable polarization states of the radiated field.

Supershaped dielectric resonator antennas

A family of dielectric resonator antennas, the supershaped DRAs, has been introduced in this communication. These DRAs exhibit wideband matching characteristics and broadside radiation. The cross section of the supershaped DRAs was described by means of a simple analytical expression depending on a set of six real parameters. By modifying these parameters it is possible to re-shape the antennas and achieve a good flexibility in terms of radiation patterns, so to match the requirements imposed by specific applications. The impedance bandwidth and the radiation patterns of the selected antennas designed to act as base-station antennas for wireless local area network systems have been simulated by means of a dedicated numerical tool based on an enhanced locally conformal finite-difference time-domain (FDTD) technique.

Compact colinear end-launcher for rectangular waveguides

A novel structure for launching the fundamental mode in rectangular waveguides is proposed. The geometry consists of a cavity-backed circular patch radiating into a rectangular waveguide. The matching properties of the proposed component are comparable with the ones of the classically used L-shaped loop end-launcher. The structure results in a very compact, colinear transition from a standard coaxial connector to a rectangular waveguide. The component has applications as general purpose coaxial-to-waveguide transition and is well suited for low-profile phased-array antennas.

Antenna pattern measurements in the V-band — a low-cost test range

A simple and cost-effective test range for the measurement of antenna radiation patterns in the F-band is described. The arrangement enables accurate antenna measurements without resorting to the use of expensive anechoic chambers. A procedure for the alignment of the antenna phase center with respect to the rotation axis of the turntable, on top of which the antenna under test is fastened, is presented. The measurement procedure has been validated by comparing the measured radiation pattern of a standard-gain horn antenna with the results predicted by means of electromagnetic analysis tools.

Wideband, multiband, tunable, and smart antenna systems for mobile and UWB wireless applications

With the advent of high data rate 3G and 4G wireless communication systems and the app-based use paradigm, wireless connectivity through multiple air interfaces has become a common requirement in the RF architecture of new generation mobile communication devices.Themodern wireless handset easily incorporates three or more antennas to enable cellular, Wi-Fi, and GPS connectivity, frequently over multiple bands. Multiple antenna systems are frequently designed to implement diversity or spatial multiplexing schemes, as in the case of WCDMA and LTE, to increase the resiliency and capacity of wireless links, and even to operate multiple voice/data links simultaneously. Concurrently, ultrawideband (UWB) systems used in short range communications, remote sensing, and through-the-wall radar imaging have introduced a new paradigm in antenna designwhere the mitigation of pulse distortion is of the essence, thus requiring a shift in antenna design approach and the introduction of novel radiating systems. This special issue is intended to reflect current R&D trends and novel approaches in the analysis and synthesis of antenna systems for the new generation of mobile communication devices, such as smartphones, tablets, and laptop computers as well as for UWB communication systems and radars. A particular emphasis has been paid to the analysis and design of broadband, multiband, and reconfigurable antennas for wireless and UWB applications, as well as to the identification of integration techniques with the host platform. Important efforts have been devoted to the characterization of the radio channel for MIMO systems. The special issue is composed of 18 contributions that can be divided into the following 8 clusters.