Leonardo Lucci

Genetic Algorithm Optimization of High-Efficiency Wide-Band Multimodal Square Horns for Discrete Lenses

By properly exciting higher order modes at an aperture it is possible to achieve higher aperture efficiencies. High efficiency antennas are mandatory in many applications, as discrete lenses, since the single element efficiency deeply affects the efficiency of the whole lens. In this contribution a genetic algorithm is applied to the mode matching analysis of square horns to achieve high radiation efficiency over a relatively wide band.

PHASE CENTRE OPTIMIZATION IN PROFILED CORRUGATED CIRCULAR HORNS WITH PARALLEL GENETIC ALGORITHMS

Achieving a high stability of the phase centre position in horn antennas with respect to frequency is a very desirable aim in reflector antenna design; a highly stable phase centre reduces efficiency dropping for defocusing at the frequency band extremes. By using an appropriate profile for the horn antenna it is possible to obtain horns both compact and with a stable phase centre. In this paper an automatic design procedure, based on Genetic Algorithms, to obtain such horns is described. The algorithm operates on many horn profile parameters, including corrugations, and is based on an accurate fullwave mode matching/combined field integral equation analysis code. To keep computing time down a full parallel algorithm over a 12 CPU parallel virtual machine is described.

A hybrid perturbative technique to characterize the coupling between a corrugated horn and a reflector dish

In this paper the electromagnetic coupling between a corrugated horn and a reflector dish is analyzed with a new hybrid perturbative technique. This coupling may produce significant modifications especially in the return loss and in the cross-polar pattern of the feed. The hybrid perturbative approach combines three different techniques: a mode matching (MM) technique for the propagation inside the horn, a method of moments (MoM) technique for the radiation of the horn taking into account the external part of the horn itself, and a fast Gaussian beam asymptotic physical optics (FGBAPO) technique for the interactions between the feed and the reflector. Some measurements and the comparison with rigorous numerical results demonstrate the accuracy of the new hybrid technique and the effects of this electromagnetic coupling on the feed performance.

A Stackable Constant-Width Corrugated Horn Design for High-Performance and Low-Cost Feed Arrays at Millimeter Wavelengths

This letter presents a design technique for circular corrugated horns for focal plane radioastronomical arrays based on the constancy of the corrugation width. The advantages of this solution are several: From the mechanical point of view, fabrication can be performed with an easy machining and low-cost processes; from the electromagnetic point of view, a careful optimization leads to high performance over the WR22 standard waveguide band.

A reconfigurable printed dipole for quad-band wireless applications

This paper is aimed at describing a low-cost, compact, nearly omnidirectional antenna working at 4 different frequencies (0.5, 0.9, 1.8 and 2.1 GHz). Several configuration of tunable antennas have been presented in the past, some indeed only on a limited frequency range, by varying lumped loads, some truly reconfigurable antennas, whose geometry is varied by solid state switches, or MEMS up to extremely flexible, and costly, MEMS-based fully reconfigurable planar antennas. Particular care must also be taken in considering the effect of the control lines for the switches, which needs to be shielded, or to be made of non conducting materials, like optical fibers to avoid negative effects on radiation. Since the latter approach is more costly, conventional control lines are used here, and their effect fully considered

Optimization of profiled corrugated circular horns with parallel genetic algorithms

Compact horns with highly stable phase centre reduce efficiency dropping for defocusing at the frequency band extremes. In this contribution an automatic design procedure for such horns, based on a parallel genetic algorithm, is described. The algorithm operates on many horn profile parameters, including corrugations, and is based on an accurate full-wave mode matching/combined field integral equation analysis code.

A Novel Design for a Circular Waveguide Directional Coupler

In this paper, a study of the coupling between a rectangular waveguide and circular waveguide is presented, aimed at developing a design procedure for a rectangular to circular waveguide directional coupler. Since radio-astronomical receivers often exploit circular horns, a coupler sharing the same waveguide type is at a premium, and furthermore, it reduces the feeding network complexity in dual polarization applications. A novel approach for obtaining traveling wave modal amplitude coefficients is presented, suitable for modes of any order. This approach is used to analyze the behavior of a single hole coupler between a rectangular and circular waveguide. From this starting point, a four holes directional coupler with good performance is designed in the 22-GHz band. Measurements and full-wave numerical simulations show excellent agreement with the proposed theory.

Design of a Smart Antenna for Mobile Ad Hoc Network Applications

Among the mobile ad hoc networks appealing characteristics there are network reconfigurability and flexibility. In this context a smart antenna capable of self-configuring multiple high-directivity beams provides a major advantage in terms of power saving, increased range, and spatial reuse of channels. In this paper a smart antenna made of a cylindrical array of patches suitable for MANETs is presented.

A Multilayer PCB Dual-Polarized Radiating Element for Future SAR Applications

The design, manufacturing, and testing of a slot-coupled multilayer dual-polarized X-band radiating element is presented. The proposed architecture provides an isolation between polarization ports better than 34 dB over a 16% frequency band. The selected technology is particularly suitable for large-scale, low-cost, and high reliable manufacturing. This work has been carried out in the frame of a research program funded by the Italian Space Agency and aimed to the development of enabling technologies exploitable in next-generation spaceborne synthetic aperture radar (SAR) antennas.

Design of a circular waveguide directional coupler at 22GHz

L. Lucci, R. Nesti, G. Pelosi, S. Selleri, and G. Tofani (1) University of Florence, Department of Electronics and Telecommunications, Via C. Lombroso 6/17 – I-50134 Florence, Italy http://www.unifi.it (2) INAF-Arcetri Astrophysical Observatory, Largo E. Fermi, 5 I-50125 Florence, Italy http://www.arcetri.astro.it (3) INAF-Institute of Radio Astronomy, via P. Gobetti, 101 – I-40129 Bologna, Italyhttp://www.ira.inaf.it