Computation of the Modes of Elliptic Waveguides with a Curvilinear 2D Frequency-Domain Finite-Difference Approach

A scalar Frequency-Domain Finite-Difference approach to the mode computation of elliptic waveguides is presented. The use of an elliptic cylindrical grid allows us to take exactly into account the curved boundary of the structure and a single mesh has been used both for TE and TM modes. As a consequence, a high accuracy is obtained with a reduced computational burden, since the resulting matrix is highly sparse

The 3D-Printed Non-Radiating Edge Gap-Coupled Curved Patch Antenna

The use of parasitic resonant patches is a widespread technique to improve the bandwidth of microstrip patch antennas. Exploiting the free form-factor allowed by 3D-printing manufacturing technology, we present here a novel curved patch antenna layout, based on the non-radiating edge gap-coupled patch configuration. The proposed antenna is composed of a central curved patch, fed by a coaxial probe, and two gap-coupled parasitic side curved patches. This solution features a percentage impedance bandwidth of 16.3% using symmetrical parasitic side patches and 31.5% using asymmetrical side patches. A significant improvement of the bandwidth in comparison with both the standard non-radiating edge gap-coupled microstrip antenna (6.1% bandwidth) and the standard curved patch antenna (9% bandwidth) is achieved. Design and optimization of the proposed configuration are performed using the commercial software CST Studio Suite at the center frequency of 2.45 GHz. Prototypes of the symmetrical curved non-radiating edge gap-coupled patch antenna have been manufactured for the experimental verification, using a curved 3D-printed polylactic acid (PLA) substrate, fabricated with the commercial 3D printer PRUSA MK3S + and a 50 μ m -thick adhesive aluminum tape for the metallization. Measured results show a very good agreement with simulations

A Novel Design for Dual-Band Wearable Textile Eighth-Mode SIW Antennas

A novel wearable textile dual-band antenna configuration based on a substrate integrated waveguide (SIW) cavity is presented. The miniaturization of the antenna is achieved by exploiting the magnetic field symmetry of a square SIW cavity, reducing its size to 1/8 of the full square cavity with an eighth-mode SIW configuration. This solution is applied to the design of a wearable dual-band antenna for Long Range (LoRa) applications. The antenna operating frequency covers both the UHF LoRa bands, the European (863-870 MHz) and the North American (902-928 MHz). The proposed design provides a low-cost and compact antenna, which is easy to fabricate and ensures a very good isolation and robustness with respect to the human body proximity. The commercial software CST Studio Suite has been used for the antenna design and simulations. A prototype has been fabricated and the measured results are in good agreement with numerical simulations

Electromagnetic analysis and performance comparison of fully 3D-printed antennas

In this work, the possibility of directly prototyping antennas by exploiting additive manufacturing 3D-printing technology is investigated. In particular, the availability of printable filaments with interesting conductive properties allows for printing of even the antenna conductive elements. Three samples of a 2.45 GHz microstrip patch antenna have been 3D-printed by using different approaches and materials, and their performance evaluated and compared. In particular, the same dielectric substrate printed in polylactic acid (PLA) has been adopted in all cases, whilst copper tape and two different conductive filaments have been used to realize the conductive parts of the three antenna samples, respectively. Even if an expected radiation efficiency reduction has been observed for the conductive filament case, the comparative analysis clearly demonstrates that 3D-printing technology can be exploited to design working fully-printed antennas, including the conductive parts

Laser scanning the Garisenda and Asinelli towers in Bologna (Italy): detailed deformation patterns of two ancient leaning buildings

The Asinelli and Garisenda towers are the main symbol of the city of Bologna (Italy). These leaning towers, whose heights are about 97 m and 48 m respectively, were built during the early 12th century and are two of the few surviving ones from about a hundred tall medieval buildings that once characterized the city. Therefore, they are part of the Italian cultural heritage and their safeguard is extremely important. In order to evaluate in detail the deformations of these towers, in particular the deviations from a regular inclination of their walls, the terrestrial laser scanning (TLS) has been used and an efficient direct analysis method has been developed. The towers have been scanned from 6 viewpoints, providing 19 point clouds with a complete coverage of the visible surfaces with large overlap areas. For each tower, after the registration of the partial point clouds into a common reference frame, an accurate morphological analysis of the acquired surfaces has been carried out. The results show several zones affected by significant deformations and inclination changes. In the case of the Asinelli tower, for which a finite element model is available, the results have also been interpreted on the basis of the static load and normal modes. The correspondence between the measured deformation and the theoretically expected deformation, caused by a seismic sequence, is clear. This fact suggests a high sensibility of the tower to dynamic loads. Although a direct evaluation of the risk cannot be carried out with the obtained results, they lead to the general indication that the structural health of these buildings must be frequently checked and that man-made loads (e.g. vibration due to vehicular traffic) should be avoided or at least reduced

A robust wearable textile SIW RFID antenna

A wearable textile Radio Frequency Identification (RFID) tag realized on a substrate integrated waveguide cavity is presented, operating in the European UHF RFID frequency band. The antenna shows a very good isolation with respect to the human body, and a satisfactory robustness to antenna-body distance variations. The resulting tag is very compact, since its size has been reduced by exploiting the symmetry of a SIW cylindrical resonant cavity and obtaining an eighth mode SIW antenna, and can be produced at low-cost through simple manufacturing processes

Linee guida per la programmazione remota e lo scarico dati di ricevitori GPS (Standard Trimble Navigation Limited - Serie 5000).

Nella fase di implementazione dell'hardware e del software per la materializzazione di stazioni GPS permanenti il problema della programmazione e scarico dati a distanza mediante modem da telefonia fissa, PSTN e ISDN o mediante modem da telefonia mobile, essenzialmente GSM /GPRS costituisce un problema di non facile soluzione. Anche laddove esista da parte delle aziende coinvolte nelle forniture un assistenza software che consenta di sviluppare dei prodotti personalizzati, alcune operazioni richieste vengono spesso eseguite dall'utenza con mezzi propri. Infatti, gli standard commerciali che vanno per la maggiore operano prevalentemente in ambiente Microsoft Windows e sono spesso privi della modularità e della flessibilità necessarie sia per adattarsi a problemi scientifici sia per la loro esecuzione in background in ambienti Unix (Linux, Solaris o HP-UX). In questo lavoro vengono analizzate le problematiche legate alla programmazione di ricevitori Trimble Navigation Limited modello 5700 CORS (Continuous Operating Reference Stations), in dotazione al Laboratorio di Geodesia e Telerilevamento dell'INGV-CNT, per un loro utilizzo nell’ambito di stazioni GPS permanenti. In particolare, è stato sviluppato un sistema automatico per il controllo a distanza, la programmazione e lo scarico dati di uno standard dei predetti ricevitori. Tutta la logistica della cascata hardware e dello strato software è stata sviluppata mediante strumenti da noi implementati; il risultato è sufficientemente stabile e può essere fattivamente utilizzato per il supporto alla realizzazione di stazioni permanenti GPS anche in siti dalla logistica scarsa come quelli situati in zone remote prive di linee telefoniche fisse e di alimentazione. Per il suddetto tipo di strumentazione infatti, non esiste in Italia una vera e propria assistenza Hardware e Software in grado di risolvere determinati problemi e, pertanto, in alcuni casi è stato necessario ricorrere sia al supporto tecnico dell'UNAVCO, il consorzio universitario Americano per il NAVSTAR GPS (http://www.unavco.org), sia alla nostra consolidata esperienza nel campo della strumentazione GPS. Il presente documento è rivolto ad un pubblico limitato costituito da quegli esperti del settore che siano interessati alla soluzione delle problematiche analizzate in questa sede

Le tecniche di indagine NDT nel processo di restauro e consolidamento di edifici soggetti a tutela

Le attività di restauro e consolidamento di edifici soggetti a tutela sono fortemente ancorate alla conoscenza del bene, alla consistenza geometrico-strutturale e a quella materica, nonché all’analisi del degrado del manufatto e del suo stato di conservazione in tutti i suoi elementi. Altri aspetti tecnici da portare in conto sono ovviamente quelli legati al monitoraggio da attuare eventualmente in fase di diagnosi e obbligatoriamente in fase di esercizio, al fine di disporre di una robusta mole di dati per governare l’attività manutentiva. Un valido supporto all’insieme di queste problematiche è offerto oggi dalle tecniche non distruttive (NDT), le quali si inseriscono sia nel processo di screening conoscitivo del manufatto che nel processo di progettazione, di realizzazione degli interventi e di vita utile del bene. In questo contesto, la presente nota illustra una panoramica di alcune delle moderne tecniche di indagine NDT impiegate nelle attività di rilievo, di valutazione dello stato dei materiali e nelle attività di monitoraggio sia propedeutiche alla redazione del progetto, sia nel corso dell’esercizio. In riferimento a quest’ultimo aspetto, le tecniche illustrate mirano ad essere parte integrante di una metodologia di controllo "routinaria" da esercitare in continuo e con la possibilità di essere interrogabile anche in tempo reale. Alcuni esempi applicativi qui riportati, seppur in forma sintetica, consentiranno di apprezzare i benefici derivanti dall'utilizzo di tecniche NDT, il cui punto di forza risiede soprattutto nel loro essere non invasive e autodiagnosticanti

Low-energy models for correlated materials: bandwidth renormalization from Coulombic screening

We provide a prescription for constructing Hamiltonians representing the low energy physics of correlated electron materials with dynamically screened Coulomb interactions. The key feature is a renormalization of the hopping and hybridization parameters by the processes that lead to the dynamical screening. The renormalization is shown to be non-negligible for various classes of correlated electron materials. The bandwidth reduction effect is necessary for connecting models to materials behavior and for making quantitative predictions for low-energy properties of solids.Comment: 4 pages, 2 figure