Antonio-D. Capobianco

Modeling of enhanced field confinement and scattering by optical wire antennas

We describe the application of full-wave and semi-analytical numerical tools for the modeling of optical wire antennas, with the aim of providing novel guidelines for analysis and design. The concept of antenna impedance at optical frequencies is reviewed by means of finite-element simulations, whereas a surface-impedance integral equation is derived in order to perform an accurate and efficient calculation of the current distribution, and thereby to determine the equivalent-circuit parameters. These are introduced into simple circuits models, directly borrowed from radio frequency, which are applied in order to model the phenomena of enhanced field confinement at the feed gap and light scattering by optical antennas illuminated by plane waves.

A Miniaturized Dual-Band MIMO Antenna for WLAN Applications

This letter reports on a compact planar dual-band Multiple-Input and Multiple-Output (MIMO) antenna for Wireless Local Area Network (WLAN) applications. The proposed antenna primarily consists of two meandered monopole radiators that are decoupled by introducing a folded Y-shape isolator element and it is shown that the edge coupling between the radiators and isolator introduces the resonance at the lower band. The miniaturization is achieved by passing the signal on to the bottom layer where a meandered line conductor introduces a broadside coupling with the radiator, originating the higher band resonance. The antenna operates between 2.4 GHz to 2.5 GHz and 5.45 GHz to 5.65 GHz with an isolation of more than 25 dB and 15 dB, respectively. The antenna measures only 19 ×23 mm2.

Frequency addressing of nano-objects by electrical tuning of optical antennas

We first analyze the equivalent circuit parameters of linear wire optical nano-antennas in uniaxial anisotropic media. We then exploit the electro-optic response of a bipolar nematic liquid crystal to demonstrate tuning of an optical antenna using a low frequency external electric field as the control mechanism.

Flared Monopole Antennas for 10-

Planar flared monopole made of nickel is proposed as an antenna for the reception of thermal radiation. The antenna partially overlaps with a ground plane; the overlapping region is supposed to host a nickel-nickel oxide-nickel diode for conversion of terahertz fields into electrical current. The antenna performance is measured in terms of enhancement of the electric field at the diode terminals. The effect of geometrical parameters on the antenna performance is parametrically investigated. A crossed-antennas scheme is finally proposed for the improvement of performance with respect to the direction of incidence and polarization state of the incoming field.

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We study the problem of optical noise growth, driven by modulation instability in fiber systems with dispersion management. We point out the role of dispersion-map asymmetry in sidebands generation nearby a pumping continuous wave, presenting a closed-form approximated theory to characterize the spectral distribution of noise. We propose some design guidelines for low-noise multi-wavelength optical systems, through an accurate prediction of noise growth in each channel, including the effects of map asymmetry and third-order dispersion.

Radiation

We perform a linear stability analysis of the Ablowitz-Biondini equations to explain the dynamic evolution of the noise squeezing, caused by the interplay among optical solitons and noise components, of initially uncorrelated statistics in fiber systems with dispersion management.

Parametric gain in fiber systems with periodic dispersion management

Excitation and propagation of spatial solitary waves due to three-wave mixing in quadratic non-linear media lead to a rich variety of interesting phenomena some of which have already experimental evidence. Analytical and numerical modelling plays a key role in gaining insight in the experimental data, in completing the theoretical understanding of the process and in predicting new possible applications. In this context, we present an extensive analytical and numerical study on the multi-parameter family of vectorial spatial solitary waves in bulk quadratic crystals. We focus our attention particularly on the threshold energy necessary to drive solitary waves on available crystals exhibiting a second order non-linearity and in describing how this threshold depends on the crystal parameters.

Noise evolution and soliton internal modes in dispersion-managed fiber systems.

In this paper, a compact planar Ultra-Wideband (UWB) antenna array with 4 monopole radiators is presented. To enhance the isolation, polarization of nearly placed elements is exploited. The proposed MIMO antenna array is electrically small 50 × 39.8 mm2, printed on a low loss 1.524 mm thick Rogers TMM4 laminate with a dielectric constant of 4.5 and a loss tangent of 0.002. Simulation in HFSS and printed prototype results satisfy the return loss requirement of better than 10 dB and isolation better than 17 dB on the entire 2.5 to 12 GHz bandwidth. The calculated envelope correlation value of less than 0.03 and the compactness of the proposed antenna array makes it suitable for small portable handheld devices.

Threshold energy of vectorial spatial solitary waves in non-linear quadratic crystals

The projection method (PM) is a simple and low-cost pattern recovery technique that already proved its effectiveness in retrieving the radiation properties of different types of arrays that change shape in time. However, when dealing with deformable beam-tilting arrays, this method requires to compute new compensating phase shifts every time that the main lobe is steered, since these shifts depend on both the deformation geometry and the steering angle. This tight requirement causes additional signal processing and complicates the prediction of the array behavior, especially if the deformation geometry is not a priori known: this can be an issue since the PM is mainly used for simple and low-cost systems. In this letter, we propose a simplification of this technique for beam-tilting arrays that requires only basic signal processing. In fact the phase shifts that we use are the sum of two components: one can be directly extracted from strain sensor data that measure surface deformation and the other one can be precomputed according to basic antenna theory. The effectiveness of our approach has been tested on two antennas: a 4 × 4 array (trough full-wave simulations and measurements) and on an 8 × 8 array (trough full-wave simulations) placed on a doubly wedge-shaped surface with a beam tilt up to 40 degrees.

A 4 element compact Ultra-Wideband MIMO antenna array

In this paper, an electrically small reconfigurable antenna fed by a co-planar waveguide(CPW) is proposed. The resonance is achieved by providing an extra path for current through additional meander lines which are attached with the main feed line. Two PIN diodes are used to reconfigure the antenna from 4.27 GHz to 3.56 GHz. The proposed antenna measures only 14.5 × 12.8 mm2 and is printed on a low loss 1.524 mm thick Rogers TMM4 laminate with a dielectric constant of 4.5 and a loss tangent of 0.002. The antenna has an omnidirectional radiation pattern at both switching frequencies with a peak gain of 1.3 dBi at 4.27 GHz and 0.2 dBi at 3.56 GHz. The proposed antenna is suitable for WIMAX and indoor wireless applications.