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

A Low-Cost Printed Log-Periodic Dipole Array for DVB-T2 Digital TV Applications

A printed log-periodic dipole array (LPDA) for DVB-T2 Digital TV applications, covering the whole DVB-T2 UHF band from Channel 21 to Channel 69 (470 MHz–860 MHz), is presented. The presented antenna offers a compact size and a lower cost compared to both wire and similar printed LPDAs, with a normalized area of only 0.26 λ2 (where λ is the free-space wavelength at the central frequency) and a similar (or higher) average gain. It is composed of meandered radiating dipoles, and it is implemented on FR4, the cheapest dielectric substrate available on the market. Moreover, the antenna size has been reduced to an A4 sheet dimension (210 mm × 297 mm) to cut down the production cost. The antenna has been designed starting from Carrel’s theory and using a general-purpose 3D CAD, CST Studio Suite. The results show that the proposed antenna can be used for broadband applications (≈74% bandwidth) in the whole operating frequency band of Digital TV, with a satisfactory end-fire radiation pattern, a stable gain, and a radiation efficiency over the required frequency range (average values 6.56 dB and 97%, respectively)

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 Wideband Single-Feed Circularly Polarized Stacked Patch Antenna

We present a circularly polarized single-feed stacked patch antenna with wide axial ratio bandwidth, suitable for both coaxial probe feeding and coplanar microstrip feeding. The antenna is composed of two patches with truncated corners connected together using four pins. The circularly polarized antenna has been designed using CST Studio Suite in the upper part of the UHF frequency band. A prototype has been fabricated using low-cost 3D-printing manufacturing technology. In this regard, both the dielectric substrate and the support for the stacked patches have been realized with a 3D-printed Polylactic Acid. Measured results provide a 34% -10 dB reflection coefficient bandwidth (between 2.14 and 3.03 GHz) and a 3 dB axial ratio bandwidth of 25% (between 2.31 and 2.97 GHz), with a flat gain in the overlapped (axial ratio-reflection coefficient) bandwidth that coincides with the axial ratio bandwidth and a peak gain of 8.5 dBic

A Compact and Robust RFID Tag Based on an AMC Structure

A platform-tolerant RFID (Radio-Frequency Identification) tag is presented, designed to operate across the entire RFID band. This tag utilizes a small Artificial Magnetic Conductor (AMC) structure as a shielding element for an ungrounded RFID tag antenna. It can be easily mounted on various surfaces, including low permittivity dielectric materials, metal objects, or even attached to the human body for wearable applications. The key features of this RFID tag include its ability to be tuned within the worldwide RFID band, achieving a maximum theoretical read range of over 11 m. Despite its advanced capabilities, the design emphasizes simplicity and cost-effective manufacturing. The design and simulations were conducted using CST Studio Suite

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