F. M. Pigozzo

Novel Design of UWB Antenna with Band - Notch Capability

An ultra-wideband (UWB) antenna with a narrow frequency notch is presented. The antenna has been fabricated on a Duroid 5870 substrate and occupies an area of only 30times35 mm2. Starting from a trapezoidal planar patch exhibiting a VSWR smaller than 2.5 in the 3.5-10 GHz band, a frequency notch at 5.65 GHz is introduced by two slots near the coplanar waveguide feeding the patch. The measured return loss shows a good agreement with the simulation results and proves that this kind of antenna is suitable for reducing the detrimental interference effects of WLAN, operating around 5.5 GHz, on UWB radio links.

A Compact MIMO Array of Planar End-Fire Antennas for WLAN Applications

An approach to the design of multiple-input multiple-output (MIMO) arrays exploiting planar directive antennas is presented. It is well known that pattern orthogonality is a key aspect to reach low correlation, and thus to improve channel capacity in rich multipath environments. However, attention is often focused on reducing mutual coupling rather than optimizing the active element patterns. In this communication a planar MIMO array of printed Yagi-Uda antennas with integrated balun is presented. The end-fire radiation mechanism of the Yagi-Uda is exploited to obtain a triangular array of three sectoral antennas. This allows to achieve nearly orthogonal patterns, while keeping a low mutual coupling among radiating elements. A properly shaped ground at the feeding points allows to increase the isolation between the antennas, even in such a compact layout. A laboratory model has been characterized experimentally, and the effectiveness of the proposed design in terms of theoretical achievable capacity is demonstrated through numerical simulations considering IEEE 802.11n multipath fading channel models.

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.

Highly directional planar ultra wide band antenna for radar applications

We describe a novel planar highly directive ultra wide band (UWB) antenna based on a disc monopole fed by a 50-Ohm microstrip line. The key feature of the proposed antenna is a careful engineering of the ground plane that permits to increase directionality for radar applications. We demonstrate through numerical simulations and measurements in anechoic chamber that the designed antenna exhibits low return loss, high directivity and good time-domain properties in the band of interest between 6 and 8 GHz.

Planar, Compact Dual-Band Antenna for Wireless LAN Applications

A compact, printed dual-band antenna for WLAN applications is proposed. The radiating elements consist of a combination of a printed dipole for the lower resonant frequency and a bow-tie antenna for the upper resonant frequency. The operation on two separate bands is guaranteed by the use of two surface-mounted-device inductors. The antenna has been manufactured in antipodal configuration. Measurement results show good omnidirectionality and low cross-polarization levels.

Nonlinear bidirectional beam propagation method based on scattering operators for periodic microstructured waveguides

Beginning with a recently proposed bidirectional beam propagation method based on scattering operators, we develop an accurate and efficient method for the analysis of periodic microstructured waveguides in a nonlinear regime. This novel numerical tool allows us to describe the role played by losses that are due to diffraction and the effects of the finite size of the beams in nonlinear optical devices with strong lateral confinement of the optical intensity. We demonstrate the effectiveness and the efficiency of our method with numerical examples.

A Planar, Differential, and Directive Ultrawideband Antenna

A novel planar differential ultrawideband antenna is described and both numerically and experimentally characterized. The proposed antenna is formed by two disc monopoles fed by 50-Ohm microstrip lines with a structured ground plane. Simulations and measurements demonstrate that it is possible to achieve a huge increase in directionality with respect to conventional monopoles by carefully engineering the ground plane and by exploiting the array effect.

Bidirectional beam propagation method for multilayered dielectrics with quadratic nonlinearity

By employing an iterative procedure based on a bidirectional beam propagation method, we develop a numerical algorithm to model light propagation in multilayered structures with second-order nonlinearities. Examples of the applicability of this technique in describing second harmonic generation in photonic crystals are given.

Second harmonic generation by modal phase matching involving optical and plasmonic modes.

The feasibility of a modal phase matching scheme between optical modes and surface plasmonic modes is demonstrated: in fact, the high effective index of a plasmonic mode allows us to obtain phase matching even in semiconductors showing a large dispersion between fundamental and second harmonic wavelengths. We design a realistic device to obtain Type-II second harmonic generation in AlGaAs-based waveguides; whereas one of the two pumps is carried by a plasmonic mode, the generated second harmonic signal is guided inside the AlGaAs multilayer, and hence it is not hampered by high propagation losses.

Bidirectional beam propagation method for second- harmonic generation in engineered multilayered waveguides

By employing an iterative procedure based on a bidirectional beam propagation method with perfectly matched layers, we develop a numerical algorithm to model light propagation in engineered multilayered nonlinear waveguides. Examples are given for multilayered structures and segmented waveguides designed for second-harmonic generation.